Added Twitter API v1.1 host and made it default host

It was a pretty simple update; however you will probably want to make some minor adjustments. I wasn't sure how to reconcile the symbol keys used in the `TWITTER_API_HOSTS` hash with the API value of v1.1. So I explicitly converted a the string "v1.1" to a simple. i.e. `'v1.1'.to_sym`