API: `Series.quantile` and `DataFrame.quantile` should have consistent arguments
`DataFrame.quantile` has a `numeric_only` keyword argument, and extends the calculation to timedelta and timestamp (not sure why str is not also included, I would suggest that a non-numeric element would typically include a string)

`Series.quantile` does not have the `numeric_only` keyword argument, and obviously doesn't work with the above dtypes.

The work around is to convert the Series to DataFrame and extract the leading column of results. 
