MNT: Update CONTRIBUTORS.md
MNT: Update CONTRIBUTORS.md

Let's just go with a list of commit authors for now.

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