Heroku Push Button

* Created an app.json for push button deploy
* Renamed the incidents dashboard to pagerduty
* Deleted the oncall dashboard and moved the elements to the pagerduty dashboard
* Modified the oncall and incidents jobs to get their data from Heroku ENV variables
* Updated Gem dependencies
Merge pull request #16 from thegreenrobot/heroku_push_button

Heroku Push Button