Fixes for local imports.
Minor syntactical changes for Python 3 compatibility (prints need parenthesis).
Move handshake out of connection thread such that creating the connection blocks until the handshake is done.
Prior to this change, Firebase refs could be created and sent over the handshake connection instead of the actual connection.  This caused several problems, including https://github.com/abeisgreat/python-firebasin/issues/3 .