Move to rails_config

@brandondunne This PR is meant to simplify the configuration of the bot.  Instead of 5 separate yml files you have to maintain, you're down to one in the rails_config style of putting everything in settings.local.yml.  This way you can manage easily with puppet.  In addition, I think the reason the issue_manager was not working is because it wasn't configured (yet another configuration file).  This PR also changes that code to look at the common yaml file.

I had to use v0.5.0.beta1 of rails_config because it has a fix for a bug when the code is not run in a Rails context (as we need to with the issue manager).

cc @jrafanie