Upgrade to use v2 api

[jonbernardi]

http://support.bugherd.com/entries/21701764-New-API-version
http://www.bugherd.com/api_v2

[drrobotnik]

Created an initial version for api_v2 based off your work and the new documentation.
https://github.com/drrobotnik/bugherd-api/blob/master/Api.php