Add github signin / signup function

[richardartoul]

Right now its a separate function because we don't have it setup everywhere properly yet, but once we do have it set up everywhere we'll change it to integrate with the login/signup commands automatically

[spence]

Really think we should use 0.0.0.0 for all hostnames in this. It's more robust in its meaning and less likely to be subject to local user environment or changes.