Got rid of body-content from jumbotron and justified-nav examples.

There is no point for extra padding on small screens because of the `body-content` since there is already some padding from the `.container` and the screen is already too small :) Plus the contents are now aligned with the `navbar-brand` :)

In the `justified-nav` example it was a left over since there was nothing in the `justified-nav.css` to clean up.

Here are both of the examples after this fix:

https://dl.dropboxusercontent.com/u/15234/bootstrap/examples/jumbotron/index.html
https://dl.dropboxusercontent.com/u/15234/bootstrap/examples/justified-nav/index.html