Add a default option to ignore aspect ratio when creating a thumbnail with FFmpeg.
Remove unused variables.
Comment as to why the default is to ignore the aspect ratio.
This fixes issue #466. You can now optionally generate thumbnails for videos with the newer versions of FFmpeg that take into account the aspect ratio.
Some minor linting.
Button should say "Regenerate Thumbnail" for clarity.
Merge pull request #468 from jgen/develop

Allow Shimmie to work with older versions of FFmpeg