Added the gifify function.

This allows to convert a .mov file into an animated GIF file. Based on
these resources:
* https://gist.github.com/SlexAxton/4989674
* https://gist.github.com/paulirish/b6cf161009af0708315c
Added two useful git aliases found here:
http://blogs.atlassian.com/2014/10/advanced-git-aliases/
Merge pull request #351 from nwinkler/git-aliases

Added two useful git aliases found here:
Merge pull request #349 from nwinkler/gifify

Added the gifify function.