Replacing IO.popen with Cocaine::CommandLine
Cocaine::CommandLine is Paperclip's wrapper for system calls and comes with a few great features:
- Testing: ``Cocaine::CommandLine.fake!`` now stubs all system calls (ffmpeg now works like Paperclip)
- Error Handling: the old command actually throws an error. It has been replaced with ``ffprobe``.
Merge pull request #37 from chip-miller/master

Replacing IO.popen with Cocaine::CommandLine