implement Model.evaluate() WIP
Merge remote-tracking branch 'cmsaunders/master'

Conflicts:
	ddtpy/fitting.py
WIP on evaluate & extract_eta_sn_sky
finish extract_eta_sn_sky, change to update_sn_and_sky
Edits to penalty fn
Merge remote-tracking branch 'kbarbary'
Finished penalty_g_all_epoch