removes security row and clarifies acceptance area

![screen shot 2014-11-25 at 15 07 13](https://cloud.githubusercontent.com/assets/5781410/5185142/c86533da-74b4-11e4-8f7b-a9d6d66447f1.png)

@jamesshedden 

The copy isn't the prettiest, but we thought about it for a while and didn't come up with anything better. Any other ideas welcome if you have them, but in the interests of time making this PR now