Bugfix: Didn't pass timeout-argument to FFMPEG

This commit fixes a bug which didn't pass the timeout configuration value to the FFMPEG Service.

A Symfony-Process has a default timeout of 300 seconds, so any transcoding-operations taking longer than 300 seconds aborted with a `ProcessTimedOutException` and `ExecutionFailureException`
Merge pull request #5 from micronax/patch-1

Bugfix: Didn't pass timeout-argument to FFMPEG