Initial username blacklist draft config

List primarily pulled from:
https://github.com/jsbin/jsbin/blob/master/config.default.json#L70-L176
(tnx @aron!)
and
http://www.quora.com/What-usernames-are-reserved-on-Twitter
and some more names I added as things came to mind.

Likely not conclusive, but certainly a start.
Merge pull request #1564 from hypothesis/username-blacklist

[WIP] Initial username blacklist draft config