pandas.date_range documentation does not have link to acceptable 'freq' values
The [API documentation for pandas.date_range](http://pandas.pydata.org/pandas-docs/version/0.15.2/generated/pandas.date_range.html) does not provide a link or explanation of the acceptable values for the 'freq' parameter, e.g. 'D' for calendar day frequency.  

There is a highly-upvoted Stack Overflow question entitled ["pandas resample documentation"](http://stackoverflow.com/questions/17001389/pandas-resample-documentation) which asks a related question about pandas.Series.resample.

The documentation for pandas.date_range should include a link to the ["Offset Aliases" section](http://pandas.pydata.org/pandas-docs/stable/timeseries.html#offset-aliases) of the timeseries documentation.
