Fix layout of Announcements form.

The form on the left sidebar is too wide. I overlaps with the contents of the page. Tested on Firefox-26. Here is a screen shot showing the problem:

![form-liquibase-org](https://f.cloud.github.com/assets/5284/1894061/6f6ed4c6-7acc-11e3-8dae-ee5f7a8d9a67.png)