Make CriticMarkup work with other bundles and other file types

Followed http://web.archiveorange.com/archive/v/DTyJuo68Dgm9lllwl14g and https://github.com/noniq/Merge-Markers.tmbundle to make CriticMarkup more general. Now it works in other bundles and other file types.

Note that I am using `L:text, source` instead of `L:source, text` because I think that CriticMarkup should match text first as it's where it'll most likely be used the most. Then match source code. Also note that `L:source, text` doesn't work well with https://github.com/streeter/markdown-redcarpet.tmbundle (the reverse order does).

Tested with https://gist.github.com/f7230384abe4d631c4e7 as shown below:
![screen shot 2014-11-18 at 1 25 07 am](https://cloud.githubusercontent.com/assets/2288213/5083315/c153b9ac-6ec1-11e4-8256-1378b00b0771.png)