DOC: add more details on selecting / indexing of time series
Add more details on selecting / indexing of time series based on dates or intervals.

to
https://github.com/pydata/pandas/blob/master/doc/source/indexing.rst
and
https://github.com/pydata/pandas/blob/master/doc/source/timeseries.rst

But I could not find any part showing how to  E.g. getting all data where year =
2004 or all data from day 2012-09-24. 

Reference:
https://groups.google.com/forum/?fromgroups=#!topic/pydata/Bt8jO2LkAdk
