Fixed small typos and CSS issues

Typo was untitiled to untitled

CSS private repo icon no longer hidden when you mouse over it.
Dropdown to choose type of file gfm/markdown/html
Allow other plugins to support different filetypes
Cleaned up Dropbox to allow new editor file types

Filters and receives correct files extensions.
Changed file type checkers to support different types

Stopped using `profile.editor.regExp` because regular expressions didn't
seem to save too well in local storage.

Moved the original file type check function into a higher scope.

By default the editor uses GFM, and has 3 file types. Because HTML has 2
file types, whenever you switch over to HTML then refresh the page,
jQuery will 'merge' the two arrays together (via $.extend) and instead
return ['.html', '.htm', '.mdown'] rather than just ['.html', '.htm']
Support views generated by pure HTML
Increment version in package.json
Switching to HTML context now requires toggling

Enabling HTML editing now requires you to toggle it in the Preferences
pane.
Set sanitize to true in marked
resolved merge conflicts