MNT: Disable running examples on AppVeyor
MNT: Disable running examples on AppVeyor

Can't figure out why running examples is failing right now, so just
disable for now so that tests don't spuriously fail.

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