Updating Twitter example to Login-v2
Facebook Support.

* Modified setup.sh to handle .pkg files, since that's how the facebook SDK is packaged.
* Added Facebook config Info.plist (and re-ordered items so URL Schemes are at the bottom,
  since you need to modify one).
* Hooked up facebook login button with super simple workflow.
Tweak setup.sh (undo some renames, remove a leftover 'zip' reference)
Ignore appcode files.
Make it clear where to put Firebase.
Merge pull request #2 from firebase/login-v2-facebook

Facebook Support.
Update to TwitterAuthHelper error handling.
Pulling out a property into a local var.
Updating providerData to new format. Changing Twitter App Id to Api Key for clarity.
Renaming twitterApiKey to apiKey in TwitterAuthHelper
Better Twitter error handling when there are no devices on the phone.
Merge pull request #3 from firebase/login-v2

Login v2