A first attemp of nicer comments

As described in #80 the comments in casper are basically a list.
![Current state of comments](https://cloud.githubusercontent.com/assets/1445869/4968251/a0330734-6839-11e4-8f8b-9c948dd56aeb.png)

I tried to improve things a little bit by reproducing the look of wp-caption for the body of the comments, and of the submit button for the reply-to.

![New Proposal](https://cloud.githubusercontent.com/assets/2682011/5424717/c8e5d9bc-82fc-11e4-91b7-d1f5f5f9ed65.png)

Let me know what you think of it !