Replace eval() with ast.literal_eval().
Replace eval() with ast.literal_eval().

literal_eval() is safer, but forces some python 2 vs. 3 nonsense on us.

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