Remove dependency on SAMCategories. #6

- Add `SimpleAuthFormSerialization`
- Move all providers and web view controllers to new serializer API.
Move to pod implementation of query string stuff.
Update query string serialization library.
Merge pull request #13 from calebd/form-encoding

Remove dependency on `SAMCategories` and add query string serialization library for all providers. Fixes #6.
Internalize some of the web view controller loading logic and simplify API.
Add Facebook web login.
Add Facebook web config to app delegate.
Move Facebook web provider to new web login api.
Parse `expires_in` to `NSDate`.
Merge pull request #14 from calebd/facebook-web

Add Facebook web login.
Update readme.
Add FacebookWeb subspec.
Add support for requesting permissions from Facebook web auth.
Change prefix on old category methods.
Link to wiki from readme.