Implement attribute start matching, ie [foo^=bar]

[rafaelw]

Moved from: https://code.google.com/p/mutation-summary/issues/detail?id=27

(from bruce.krysiak)
I want to observe elements with attributes starting with a certain string. These may not be whitespace-separated, and I only want to match at the start - normal CSS matching like [foo^=bar]

I have a clone implementing this, but the instructions for how to request a pull/merge are very nonexistent. Any suggestions? I'm happy to update the wiki too once it's in if you like.

Thanks, great work on this library. Hope you don't mind my reversing some test assertions to match the mocha signatures in order to get better test failure messages.

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Actually, it wasn't too hard to also throw in the rest of the missing attribute selectors:

[foo$=bar]
[foo*=bar]
[foo|=bar]

I almost skipped the hyphen matcher, but since I did the rest I figured it was worthwhile. The others seem valuable at least. All in the same cloned repo: https://code.google.com/r/brucekrysiak-mutation-summary/source/browse