Ensuring ffmpeg installation

[morsh]

Hi,
I wanted to use ffmpeg as part of a continuous deployment strategy.
To do that I need ffmpeg to be installed automatically.

I guess that ffmpeg installation is a prerequisite for usage of this module since it's a large file.
I'd be happy to submit a PR that ensures ffmpeg is installed on a local machine (by exposing an "ensureInstallation()" method).

For a linux machine, this might be less of a problem, since you can run apt-get on shell.
But on a windows machine, this would require downloading the ffmpeg zip file, extracting it, and exposing the ffmpeg.exe file (including the other exe files).

WDYT?

[SilverGhostBS]

Personally I think the constructor:

const ffmpeg = new ffmpeg(videofile)

should throw an exception if ffmpeg is not installed. The generated object is completely and utterly useless if ffmpeg is not there.