implement immediate callback
Merge branch 'immediate' of github.com:tellnes/oauth2orize into tellnes-immediate
Refactor immediate mode callback for style and extensibility.
Add TokenError class.
Use token error in authorization code exchange.
Export TokenError.
Use token error in token middleware.
Use token error in exchanges.
Add test cases for TokenError.
Capitalize Bearer, as that seems to be the emerging convention.
Test cases for immediate mode callback.
Test cases for immediate mode callback error handling.
Test case for immediate callback with scope.