Tahi-project/tahi — pull request #526 by neo-tahi (2014-10-23 13:21:16+00:00)
Title: Ensure that task_type param is an allowed TaskType

# References
* https://www.pivotaltracker.com/story/show/80334890

# Notes
* We really need an authoritative source for what are valid/allowed task types. We essentially have that in our `TaskType` factory except for one lone holdout, the good 'ol `MessageTask`. I decided to add it with these changes so that we can allow it to be verified before creation.