Bitbucket Importer requested to merge bitbucket/merged-pr-2 into branch/default Oct 30, 2017

Created originally on Bitbucket by calpe (Miguel Calpe)

Was already merged in Bitbucket before import, marked as merged by the import user

Solved bug in output.phys_fields.animate.

New function _select_key_field. If key_field is None, it chooses one from key_state_phys.
If key_field is given by the user, it checks if key_field is in key_state_phys.

New variable tmin: to make video from tmin to tmax.

make tests ok!