Fix typo in error message
Merge pull request #53 from mekza/fix_typo

Fix typo in error message
Introduced FFMPEG_BINARY in ffmpeg_tools. Fixes critical Windows error.
Merge branch 'master' of https://github.com/Zulko/moviepy
changed padding in concatenate. Added slide_in/out transitions (not tested)
Big rewrite of the docs
changed to_videofile->write_videofile etc.  Factorized verbose_print
added subtitles. other changes in gallery, videoclip, compositevideo
added experimental side-in/out transitions
Merge branches, fixed to_gif

Conflicts:
	moviepy/video/VideoClip.py
fixed quality/fps  in write_gif2. added __str__ in subtitles
added "interactive show". Add 'r' before paths in conf.py. Rewrote crash course