Use GitHub for login

[hawkowl]

How you can test this:

• set up your vagrant vm like usual (base.bootstrap, t-web.install, trac.install, t-web.start, trac.start)
• make some fake tls keys (t-web.makeTestTLSKeys, t-web.installTLSKeys)
• set 172.16.255.140 twistedmatrix.com in your hosts file
• go to https://github.com/settings/developers , register a new application, put the client ID in services/trac/trac-env/conf/trac.ini right at the bottom -- the one in there right now is the prod ID
• ssh in to the vagrant vm, sudo su trac; mkdir ~/secrets; cat $THEIDSECRET > ~/secrets/secret.txt
• go to https://twistedmatrix.com/trac/ , click on the 'github login' button... you should be logged in!

Works on my instance :D

[mithrandi]

👍 (I have not tested this locally, but I did review the diff)