Merge of main bootstrap-wysihtml5 (Merge pull request #233 from shaunfreeman/dev) with pull request (Inserting YouTube videos) with the commit from elzos (commit: fc37019)

Added youtube video support.
Addition of highlight.js support through button in editor.
Updates to documentation in index.html

Highlight.js support merged from fork of bootstrap-wysihtml5 on github by evereq
https://github.com/evereq/bootstrap-wysihtml5
merge was taken from commit 518d40d57821413047b1560a7cb52c82a409fab7
and merged with head with minor updates from original code.
File upload support.
When `options.fileUpload` is provided, there will be an additional file input field in the insert image modal.
Whenever a file is uploaded, it **alt** or **src** will be append to the modal.
Add file-upload section to readme.
Issue #1 - Set the drag & drop zone to the entire modal.
I added a sentence `locale.en.image.usage`. Other language supports should be added.
Fixed the bug that after inserting images, the `.uploaded` section is not reset.
Chinese support on issue #1.
Merge fork puredistortion/master
Merge fork trantorLiu/file-upload with conflicts
Manual merge fork cmdalbem/patch-2