Add ability to ignore certain words/regexp in diff

[watzon]

This may be an edge case, but often when I'm diffing two files they both have suffixed names like CC_IndexController_CW inside. These suffixes always differ and end up adding tons of false positives in my diffs. It would be nice if we could ignore certain patterns so I don't run into this

[mupchrch]

I don't think the diff library I am using supports ignoring certain patterns. So the only solution I can think of would probably cause word highlighting to mess up and not be aligned properly. I'll definitely keep thinking about it though.