ENH Brain: allow time_label to be function

[christianbrodbeck]

This should solve the problem of displaying time in ms while representing it in seconds (which is assumed by Brain.save_movie() when determining time dilation). To display in ms use time_label=lambda x: '%s ms' % int(round(x)).

[agramfort]

LGTM

[coveralls]

Coverage increased (+0.04%) to 72.49% when pulling cad4820 on christianbrodbeck:timelabel into a7b4097 on nipy:master.

[coveralls]

Coverage increased (+0.04%) to 72.49% when pulling cad4820 on christianbrodbeck:timelabel into a7b4097 on nipy:master.

[coveralls]

Coverage increased (+0.04%) to 72.49% when pulling cad4820 on christianbrodbeck:timelabel into a7b4097 on nipy:master.

[larsoner]

Thanks @christianbrodbeck!