Added 'add_timestamp' to the isentropic_example.py file
Added 'add_timestamp' to the isentropic_example.py file

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