Switching trainee status to enumerated field
Cohort details page shows participants with status
Bug fix: cohort venues not being recorded correctly.

1. Fixed bug in `migrater.py`: cohort venues were being stored as strings, not site IDs.
2. Updated db.sql to match.
migrater.py: Use datetime.date.today() to find the current date

Instead of hardcoding it in the Makefile.  This reverts the portion of
4c6fa04b (Switching trainee status to enumerated field, 2014-12-15)
that added the TODAY argument.

The .isoformat() call is because I don't know if cohort_start[cohort]
is a string or a datetime.date.  Since we were using string
comparisons before, using a string here seemed safer.
Merge pull request #4 from wking/get-today-automatically

migrater.py: Use datetime.date.today() to find the current date
Merge pull request #78 from gvwilson/defining-enumeration-for-instructor-training-status

Defining enumeration for instructor training status