A start on video thumbnailing; see #400

Almost certainly not working yet; not tested, just committing so that
other people have something to work with and we aren't duplicating
effort
Working on thumbnail support for video files.
Video thumbs are working for webm files now.
Fix indentation (spaces -> tabs)
Added conditional message for IE users to download plugin from Google for webm.
Merge pull request #406 from jgen/video_thumb

Video thumbnails
Code Removal: PHP has had JSON support directly baked into the language since 5.2.0 - there is no need to rely on an external library from 2006 for json support.
Removing this file.
Merge branch 'linting' of github.com:jgen/shimmie2 into code_removal
Merge branch 'video_thumb' of git://github.com/shish/shimmie2 into develop
Merge branch 'code_removal' of github.com:jgen/shimmie2 into develop