Upgrade to hipchat API version 2, support python3.

Hipchat handler used deprecated Hipchat API (version 1). I've upgraded code to support current API version 2. 

Also previous code didn't work in python3 as `urllib.urlencode()` method was moved to `urllib.parse.urlencode()` (see http://docs.pythonsprints.com/python3_porting/py-porting.html). This problem is solved as side effect of API upgrade.