Adding new user_ip(uip) and user_agent(ua) params

- Params added to GA on Feb 14, 2014
- See https://groups.google.com/forum/#!msg/google-analytics-measurement-protocol/8TAp7_I1uTk/CIJtk3W3L-UJ
Merge pull request #15 from medullan/master

Adding new user_ip(uip) and user_agent(ua) params