Added configurable HIDDEN_STACKTRACE_MODULES

[DrMeers]

Using dirname on SocketServer was wiping out all of the system libraries from the stacktrace, since it is a single-file module unlike Django.

But it is also nice to be able omit things like gunicorn, threading, newrelic, etc as required -- otherwise the DOM structure generated for the stack trace blows out to impractically large proportions with a large number of queries.

May be nice to also add regex filter capabilities for modules which cannot be imported (e.g. gunicorn entry points)

[aaugustin]

I've updated your patch to apply cleanly on master and support Python 3. I've pushed it in 5b1fd5a. Thanks for your contribution.

Tests would have been a plus. If I hadn't performed some last-minute manual testing under Python 3, I would have pushed code that didn't work under Python 3 (because map returns an iterator). If you added tests now, that would be much appreciated. Thank you.

[aaugustin]

If you submit another pull request, please add yourself to AUTHORS too :)

[DrMeers]

Thanks Aymeric, great to see this repository coming back to life. Yes, I only had time to go so far as making sure none of the existing tests failed. Have added writing specific tests for this to my TODO list, but don't hold your breath!

[aaugustin]

I know... ;-)