change name of big bg img on home screen
Add more background images. Randomize which to show.

However, I am not sure that the `rand()` function used allows
the highest integer provided to be shown. Potential bug!
Add navigation. Transparent bg on home. Not yet responsive.
Add title helper

This adds the ability to customize the title in the views. By simply
doing `<% title "Lolfesten" %>` in a view, the `<title>` attr in
the head is changed.