added ability to skip analytical jaobian generation (as it can take quite a long time)
added ability to skip analytical jaobian generation (as it can take quite a long time)

Signed-off-by: Nick-lab <622d027d744d44ccdd4ef2590cf38294038f753b@uconn.edu>

kyleniemeyer/pyJac,SLACKHA/pyJac,SLACKHA/pyJac,kyleniemeyer/pyJac