Rename OAuth facade

[adamwathan]

Conflicts with a reasonably common PHP extension.

[dusterio]

Does it matter – the alias is 'SocialAuth' anyway?

[adamwathan]

Yeah updating the docs to recommend aliasing it as SocialAuth was sort of a quick workaround in the mean time. I think it's a better name overall regardless, the name of the package is sort of regrettable at this point even, haha...