Minor copy editing
Minor copy editing

A few light editorial fixes. Notes:

* “Setup” is a noun; “set up” is a verb.
* In the latest Swift, you can do “if let authToken = authToken” to unwrap an optional using the same var name. If you want to keep the separate variable name, “optional” has just one “n”.

Thanks for the project. Looking forward to trying it out!
crousselle/SwiftOAuth2