Allow custom Oauth Providers

[zspencer]

Connects #48

@perrybutler - This was a relatively quick/hacky way to put together a generic custom oauth provider. There's still some stuff that'soutstanding that may be worth poking at:

1. [ ] Programatically figure out if we need to add a ? at the end of the urls or something; right now we have to remember to set them (or not).
2. [ ] Allow configuration for json vs query param implementations.
3. [ ] Make whether to look for expires_in/expires_at in the response configurable
4. [ ] Allow Customization of what the provider is called in the providers list
5. [ ] Document how to use it/set it up.

[danielabbatt]

Any chance of getting this merged?

[stephandesouza]

Hey @perrybutler any change to get this plugin maintained?