Pagerduty module additions

These changes will likely break old pagerduty tasks but is much easier and cleaner to use now, with a few new features. Tested with test_module and in a production environment. 

Added:
- ability to end maintenance windows with the 'stopped' state
- token auth (requester_id defaults to user)
- set minutes when creating a maintenace
- lookups for service ID and user ID
- implemented 'changed' logic
- added error handling to PD API calls

Changed:
- 'user' is now user's name or email, no longer need to know ID
- 'service' is now the service name, no longer need to know ID
- removed redundant 'running' state