Use HTML5 canvas detection instead of browser sniffing.

git-svn-id: https://plugins.svn.wordpress.org/better-file-editor/branches/development@813347 b8457f37-d9ea-0310-8a92-e5e31aec5664
Merged latest development 2.1.2 release into trunk.

git-svn-id: https://plugins.svn.wordpress.org/better-file-editor/trunk@813349 b8457f37-d9ea-0310-8a92-e5e31aec5664