style tweaks for exhibit contacts

With `col-md-6`, there wasn't enough space in the first input field to see my email address. I've tried to fix that, and tweak the margin for those contacts.

![screen shot 2014-02-27 at 12 38 15](https://f.cloud.github.com/assets/111218/2287643/539f9d32-9fef-11e3-902b-d3b63237a734.png)
![screen shot 2014-02-27 at 12 39 55](https://f.cloud.github.com/assets/111218/2287644/53aec9e2-9fef-11e3-9dc6-0e2e3a79ff3b.png)