Brain.save_movie() II

Alternative to https://github.com/nipy/PySurfer/pull/79 co-opting `Brain.make_montage()`

That looks much nicer :) I think I'd prefer 30. or 60. (and a float in any case) for the framerate, any reason to go with 25? Is this a NTSC vs PAL thing? If so, I think NTSC should win because it's a higher number :)