Tweak some doc formatting options.
Tweak some doc formatting options.

Change how napoleon handles return type. Also change how autodoc formats
the main class docstring.

Unidata/MetPy,dopplershift/MetPy,jrleeman/MetPy,deeplycloudy/MetPy,Unidata/MetPy,ahill818/MetPy,ShawnMurd/MetPy,ahaberlie/MetPy,ahaberlie/MetPy,dopplershift/MetPy,jrleeman/MetPy