Merge pull request #16 from wannabefro/master

Add Firebase.update to readme.md
Merge pull request #18 from wannabefro/master

Add in ability to create instances of Firebase
Make Firebase::Request thread safe

Refactor Firebase Request to no longer rely on instance variables set by
the firebase class
Fixed bug when setting the base_uri on a Firebase Instance
Merge pull request #2 from wannabefro/thread

Make Firebase::Request thread safe