Start/End event

![image](https://cloud.githubusercontent.com/assets/8709555/5211910/977b1b1c-75b9-11e4-91e6-174fd93414a4.png)

1. Can edit closed event
2. Can start event (after entering start amount)
3. Can end event (after entering end amount)

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why not put this logic into EditEventForm instead so that it can make sure it returns a valid date instead of having to check for it here twice