Don't load roles.coffee if using auth.coffee

This will not load roles.coffee if HUBOT_AUTH_ADMIN is set, this assumes you are
using auth.coffee if it is set.

Fixes #518
Simplify version parsing
Remove tweet.coffee from hubot-scripts.json

Requires users to add the ntwitter to package.json which is a hurdle to simply deploying to heroku.

Fixes #527
remove `Response#http` deprecation
Merge branch 'master' into vthree-rethink

Conflicts:
	src/scripts/roles.coffee