Fix __repr__ when MediaFormatInfo().duration is None
README: fix incorrect syntax in the quickstart example

Thanks to Thijs Triemstra for reporting the problem.
Merge pull request #36 from senko/fix-quickstart-example

README: fix incorrect syntax in the quickstart example
Merge pull request #40 from tahajahangir/master

Fix __repr__ when MediaFormatInfo().duration is None
Merge pull request #33 from cytec/development

Development
Merge pull request #42 from cytec/development

fix ffmpeg for travis
Add a process pid when extiting with FFMpegConvertError.
Merge pull request #44 from KoleS46/master

Add a process pid when extiting with FFMpegConvertError.