Fix columns

This PR fixes #38 (the layout issue in which the width of the page is messed up).

This PR changes some bootstrap HTML components to utilize the columns properly, this ensures the page looks good in all sizes (with or without a sidebar).

Here's a screenshot:

![](http://i.imgur.com/X93s7Uc.png)

As you can see, the right side of the page will never overflow :)

There is one drawback here, however, in order to make this work 'cleanly', we can't use a fixed sidebar which is sticky down the page. After thinking about it however, I think that's actually fine for us, since we only display the sidebar on large screens anyway -- which means the user can scroll easily.

Hopefully this makes sense.