adjust layout of graphs-view for bootstrap3.

This should fix #306 as it displays a graph view like this:
(also button are displayed like buttons again - the ominous `btn-default` class)

![graph_view_bootstrap3](https://f.cloud.github.com/assets/697338/1380027/ab244abe-3afd-11e3-9f59-3826dce752a6.png)