Adds red outlines to invalid custom form elements

Before:
![screen shot 2014-11-19 at 5 36 13 pm](https://cloud.githubusercontent.com/assets/186715/5118160/e31947e4-7012-11e4-9fbc-64b3fa3d33ef.png)

After:
![screen shot 2014-11-19 at 5 10 31 pm](https://cloud.githubusercontent.com/assets/186715/5118161/e74f5f6a-7012-11e4-86be-df5da1ae7606.png)

Before:
![screen shot 2014-11-19 at 5 37 06 pm](https://cloud.githubusercontent.com/assets/186715/5118162/ec2a6a66-7012-11e4-85af-230558d2650b.png)

After:
![screen shot 2014-11-19 at 5 34 43 pm](https://cloud.githubusercontent.com/assets/186715/5118163/f03cf790-7012-11e4-90cf-de6aa791bf9c.png)