Add Auth0 umbrella header.

Added header for Core and UI subspecs too.
Update README.
Refactor dynamic font loading.
Refactor how to auth with a social strategy.
Fix issue with twitter callbacks.

Now you dont need to specify a callback URL for twitter. It will use
a0<ClientID>://twitter.auth0.com/authorize.
Update README

[skip ci]
Fix build and further README updates.
Start moving examples folder.
Renamed examples folder.
Fix travis build.
Merge pull request #26 from auth0/chore-umbrella-header

Add umbrella header for SDK