new branch to fix event_occurences bug. Pivotal #:76544670

new branch to fix event_occurences bug.
Pivotal #:76544670, https://www.pivotaltracker.com/n/projects/982890/stories/76544670
repeating event schedule is not respecting end time limit (event.repeat_ends_on)
Fixes repeating event repeat_ends_on bug by modifying the next_occurrences function to only accept scheduled event instances before that datetime.
Use constants instead of class variables: `COLLECTION_TIME_FUTURE`