attach and view a proof for a particular standard

* add ability to attach one proof for one standard with integration
tests
* restrict proof route to everything but index
* redesign homepage and users#show page

![screenshot 2014-03-05 16 53 33](https://f.cloud.github.com/assets/331004/2339043/a04f67c8-a4b0-11e3-9c5e-470f21776d58.png)