Tweak messaging and secondary field sizes 

* Increase vertical space for transaction fields. Intro paragraph boxes were too short, making it hard to write and
review the content.
* Tweak "can't edit" messaging

Depends on #320 being merged for admin gem bump.

## Before
![screen shot 2014-12-04 at 10 56 22](https://cloud.githubusercontent.com/assets/319055/5297200/5a7441a8-7ba4-11e4-89ef-02d7e8c8cdef.png)

## After
![screen shot 2014-12-04 at 10 55 02](https://cloud.githubusercontent.com/assets/319055/5297202/5d8fbdc2-7ba4-11e4-970f-c0095afb812b.png)
![screen shot 2014-12-04 at 10 53 45](https://cloud.githubusercontent.com/assets/319055/5297203/5da219ea-7ba4-11e4-8328-01a43f1e4125.png)