most of the tests (rspec and cucumber) working after event_instance migration and new start/heartbeat fields

most of the tests (rspec and cucumber) working after event_instance migration and new start/heartbeat fields
Please give me feedback, so we can wrap this up & move to the next step in the Epic
https://www.pivotaltracker.com/n/projects/982890/stories/79396006
What is 'heartbeat'?