Add Styling to Admin Metabox Textarea Fields

The textarea fields on the `Form Settings` page have no default styling and don't look the best. It's probably a good idea to set some default and then let the textareas override them with classes if they don't like the defaults.

**Before**
![no-textarea-styling](https://f.cloud.github.com/assets/1065372/1608728/de4cda4a-5511-11e3-9d21-82c5a30db387.png)

**After**
![textarea-styling](https://f.cloud.github.com/assets/1065372/1608731/e6aac1a2-5511-11e3-9864-84d1cbf85d2a.png)