Update deprecated form selectors (:file, :radio, etc.)

Shorthand form selectors in jQuery such as :file, :radio, :checkbox and others have been deprecated. I've replaced any instances with the standard type which has always been supported. For example, :file now is input[type=file]. There are a few instances in rails.js where this was already being done so I stuck to the same format (no quotes on attribute value).

Deprecation details: http://api.jquery.com/category/deprecated/.
Form selector deprecation ticket: http://bugs.jquery.com/ticket/9400

Using the standard selector (e.g. input[type=file]) provides better performance in modern browsers.