Resample function documentation does not explain 'how' argument 
Current documentation for resample function does not document 'how' argument:

[Resample documentation](https://pandas.pydata.org/pandas-docs/stable/generated/pandas.DataFrame.resample.html)

Previous versions of Pandas did document this argument:

[Old resample documentation](https://pandas.pydata.org/pandas-docs/version/0.17/generated/pandas.DataFrame.resample.html)
