Fix validation error type `SS02` and check in CI
#### Problem description
In order to have a continuous check by the CI on validation error `SS02` (Summary does not start with a capital letter), fixing them in the code base enables the addition to the CI for automated testing in the future.

`SS02` has just 61 occurrences (see [overview of the errors](https://gist.github.com/198cfa552c727d71bd7360fda66fdbb4)):

method | file | file_line | github_link
-- | -- | -- | --
pandas.tseries.offsets.DateOffset.normalize | None | NaN | https://github.com/pandas-dev/pandas/blob/master/None#LNone
pandas.tseries.offsets.BusinessDay.normalize | None | NaN | https://github.com/pandas-dev/pandas/blob/master/None#LNone
pandas.tseries.offsets.BusinessHour.normalize | None | NaN | https://github.com/pandas-dev/pandas/blob/master/None#LNone
pandas.tseries.offsets.CustomBusinessDay.normalize | None | NaN | https://github.com/pandas-dev/pandas/blob/master/None#LNone
pandas.tseries.offsets.CustomBusinessHour.normalize | None | NaN | https://github.com/pandas-dev/pandas/blob/master/None#LNone
pandas.tseries.offsets.MonthOffset.normalize | None | NaN | https://github.com/pandas-dev/pandas/blob/master/None#LNone
pandas.tseries.offsets.MonthEnd.normalize | None | NaN | https://github.com/pandas-dev/pandas/blob/master/None#LNone
pandas.tseries.offsets.MonthBegin.normalize | None | NaN | https://github.com/pandas-dev/pandas/blob/master/None#LNone
pandas.tseries.offsets.BusinessMonthEnd.normalize | None | NaN | https://github.com/pandas-dev/pandas/blob/master/None#LNone
pandas.tseries.offsets.BusinessMonthBegin.normalize | None | NaN | https://github.com/pandas-dev/pandas/blob/master/None#LNone
pandas.tseries.offsets.CustomBusinessMonthEnd.normalize | None | NaN | https://github.com/pandas-dev/pandas/blob/master/None#LNone
pandas.tseries.offsets.CustomBusinessMonthBegin.normalize | None | NaN | https://github.com/pandas-dev/pandas/blob/master/None#LNone
pandas.tseries.offsets.SemiMonthOffset.normalize | None | NaN | https://github.com/pandas-dev/pandas/blob/master/None#LNone
pandas.tseries.offsets.SemiMonthEnd.normalize | None | NaN | https://github.com/pandas-dev/pandas/blob/master/None#LNone
pandas.tseries.offsets.SemiMonthBegin.normalize | None | NaN | https://github.com/pandas-dev/pandas/blob/master/None#LNone
pandas.tseries.offsets.Week.normalize | None | NaN | https://github.com/pandas-dev/pandas/blob/master/None#LNone
pandas.tseries.offsets.WeekOfMonth.normalize | None | NaN | https://github.com/pandas-dev/pandas/blob/master/None#LNone
pandas.tseries.offsets.LastWeekOfMonth.normalize | None | NaN | https://github.com/pandas-dev/pandas/blob/master/None#LNone
pandas.tseries.offsets.QuarterOffset.normalize | None | NaN | https://github.com/pandas-dev/pandas/blob/master/None#LNone
pandas.tseries.offsets.BQuarterEnd.normalize | None | NaN | https://github.com/pandas-dev/pandas/blob/master/None#LNone
pandas.tseries.offsets.BQuarterBegin.normalize | None | NaN | https://github.com/pandas-dev/pandas/blob/master/None#LNone
pandas.tseries.offsets.QuarterEnd.normalize | None | NaN | https://github.com/pandas-dev/pandas/blob/master/None#LNone
pandas.tseries.offsets.QuarterBegin.normalize | None | NaN | https://github.com/pandas-dev/pandas/blob/master/None#LNone
pandas.tseries.offsets.YearOffset.normalize | None | NaN | https://github.com/pandas-dev/pandas/blob/master/None#LNone
pandas.tseries.offsets.BYearEnd.normalize | None | NaN | https://github.com/pandas-dev/pandas/blob/master/None#LNone
pandas.tseries.offsets.BYearBegin.normalize | None | NaN | https://github.com/pandas-dev/pandas/blob/master/None#LNone
pandas.tseries.offsets.YearEnd.normalize | None | NaN | https://github.com/pandas-dev/pandas/blob/master/None#LNone
pandas.tseries.offsets.YearBegin.normalize | None | NaN | https://github.com/pandas-dev/pandas/blob/master/None#LNone
pandas.tseries.offsets.FY5253.normalize | None | NaN | https://github.com/pandas-dev/pandas/blob/master/None#LNone
pandas.tseries.offsets.FY5253Quarter.normalize | None | NaN | https://github.com/pandas-dev/pandas/blob/master/None#LNone
... | ... | ... | ...
pandas.tseries.offsets.Tick.normalize | None | NaN | https://github.com/pandas-dev/pandas/blob/master/None#LNone
pandas.tseries.offsets.Day.normalize | None | NaN | https://github.com/pandas-dev/pandas/blob/master/None#LNone
pandas.tseries.offsets.Hour.normalize | None | NaN | https://github.com/pandas-dev/pandas/blob/master/None#LNone
pandas.tseries.offsets.Minute.normalize | None | NaN | https://github.com/pandas-dev/pandas/blob/master/None#LNone
pandas.tseries.offsets.Second.normalize | None | NaN | https://github.com/pandas-dev/pandas/blob/master/None#LNone
pandas.tseries.offsets.Milli.normalize | None | NaN | https://github.com/pandas-dev/pandas/blob/master/None#LNone
pandas.tseries.offsets.Micro.normalize | None | NaN | https://github.com/pandas-dev/pandas/blob/master/None#LNone
pandas.tseries.offsets.Nano.normalize | None | NaN | https://github.com/pandas-dev/pandas/blob/master/None#LNone
pandas.tseries.offsets.BDay.normalize | None | NaN | https://github.com/pandas-dev/pandas/blob/master/None#LNone
pandas.tseries.offsets.BMonthEnd.normalize | None | NaN | https://github.com/pandas-dev/pandas/blob/master/None#LNone
pandas.tseries.offsets.BMonthBegin.normalize | None | NaN | https://github.com/pandas-dev/pandas/blob/master/None#LNone
pandas.tseries.offsets.CBMonthEnd.normalize | None | NaN | https://github.com/pandas-dev/pandas/blob/master/None#LNone
pandas.tseries.offsets.CBMonthBegin.normalize | None | NaN | https://github.com/pandas-dev/pandas/blob/master/None#LNone
pandas.tseries.offsets.CDay.normalize | None | NaN | https://github.com/pandas-dev/pandas/blob/master/None#LNone
pandas.Timestamp.ceil | None | NaN | https://github.com/pandas-dev/pandas/blob/master/None#LNone
pandas.Timestamp.combine | None | NaN | https://github.com/pandas-dev/pandas/blob/master/None#LNone
pandas.Timestamp.floor | None | NaN | https://github.com/pandas-dev/pandas/blob/master/None#LNone
pandas.Timestamp.fromordinal | None | NaN | https://github.com/pandas-dev/pandas/blob/master/None#LNone
pandas.Timestamp.fromtimestamp | None | NaN | https://github.com/pandas-dev/pandas/blob/master/None#LNone
pandas.Timestamp.replace | None | NaN | https://github.com/pandas-dev/pandas/blob/master/None#LNone
pandas.Timestamp.strftime | None | NaN | https://github.com/pandas-dev/pandas/blob/master/None#LNone
pandas.Timestamp.strptime | None | NaN | https://github.com/pandas-dev/pandas/blob/master/None#LNone
pandas.Timedelta.view | None | NaN | https://github.com/pandas-dev/pandas/blob/master/None#LNone
pandas.Timedelta.ceil | None | NaN | https://github.com/pandas-dev/pandas/blob/master/None#LNone
pandas.Timedelta.floor | None | NaN | https://github.com/pandas-dev/pandas/blob/master/None#LNone
pandas.Timedelta.to_pytimedelta | None | NaN | https://github.com/pandas-dev/pandas/blob/master/None#LNone
pandas.HDFStore.groups | pandas/io/pytables.py | 1093.0 | https://github.com/pandas-dev/pandas/blob/master/pandas/io/pytables.py#L1093
pandas.Panel.items | None | NaN | https://github.com/pandas-dev/pandas/blob/master/None#LNone
pandas.Panel.major_axis | None | NaN | https://github.com/pandas-dev/pandas/blob/master/None#LNone
pandas.Panel.minor_axis | None | NaN | https://github.com/pandas-dev/pandas/blob/master/None#LNone

Todo:
* [ ]  get rid of the errors in the code base
* [ ]  update the `code_check.sh` script to take into account the `SS02` type of errors