Make layout responsive for mobile devices

Created by: nihathrael

Hi everyone, I've added a small line to enable the mobile layout capabilities of Bootstrap. This way the site is much more enjoyable to read on mobile phones/tablets and still looks the same on desktops.

Of course, a number of additional things could be improved (download button layout, responsive menu, etc.), but I think this solves 95% of all mobile problems so far.

Cheers, Thomas