UX: improve readability of video titles in lazyYT oneboxes

This PR adds background to video titles in lazyYT oneboxes.

Some titles were just painful to read, especially on a bright background.
I tried to follow the visual style of already present button so that it looks natural.

**Before/After:**
![2014-09-23-215920_557x311_scrot](https://cloud.githubusercontent.com/assets/157609/4379156/3104408a-435e-11e4-99c0-fb5a6616ec53.png)