Fixed positioning of the 'Delete annotation category' button

Repositioned the button so it fit better with the layout at higher resolutions.

Before:
![screen shot 2013-10-05 at 10 21 01 pm](https://f.cloud.github.com/assets/817212/1276071/8719d164-2e2f-11e3-8d6e-e52f41e167ce.png)

After:
![screen shot 2013-10-05 at 10 26 09 pm](https://f.cloud.github.com/assets/817212/1276072/8726745a-2e2f-11e3-8408-dbcbc4ee190a.png)