Post items styling

Centered form
Added input highlighting
Styled button to be consistent with rest of site
Sized form inputs
![screen shot 2013-09-12 at 2 53 23 pm](https://f.cloud.github.com/assets/2581954/1133852/70a0d29a-1be5-11e3-936a-f42076dc8f55.png)
![screen shot 2013-09-12 at 2 53 38 pm](https://f.cloud.github.com/assets/2581954/1133853/72543474-1be5-11e3-9a8e-29c31e2b3fd8.png)