Ruby 2.x.x compatibility and Pusher Protocol 7 Support

Bumped dependency versions. Fixed errors with new versions and made all tests pass.
Tested on 1.9.3-p545, 2.0.0-p451, Ruby 2.1.1

###### Pusher Protocol 7
Added new option to specify Activity Timeout, which is now exposed with the handshake  #127 #126