Build a 7.x-2x version with the Mixpanel PHP Library

Mixpanel released their PHP library last month and it has an examples folder with some pretty good examples of how to use it. It may be beneficial to consider a rewrite of the module using this library, and I'd be more than willing to help out with it, just let me know if you feel that's a good direction to move in. You can read some docs on the library at https://mixpanel.com/help/reference/php and download it from github at https://github.com/mixpanel/mixpanel-php .

Again, let me know if you think this is a good direction and if you would like some help with it I can start a proof of concept this week. I think this would simplify the module and make it a little easier to add future functionality.