support login with IdP access_token
Update README.md
Update README.md
typo
Add Cocoapods support.

Create podspec file.
Add Example project w/ Cocoapods.

Cloned NativeLoginSample project but now it uses Cocoapods (for Auth0CLient &
FacebookSDK).
Updated README.md to include CocoaPods support.
Merge pull request #14 from auth0/feature-cocoapods

CocoaPods support