Add new plot elements to Skew-T example.
Add new plot elements to Skew-T example.

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