Remove check boxes on channels page

* On the channels page: https://go.vumi.org/channels/
* selecting the checkboxes and then clicking the 'release' button in the header doesn't do anything.
* this is freaking out our beta users
* let's kill the checkboxes and release button and remove them from the UI

![screen shot 2013-08-29 at 4 55 22 pm](https://f.cloud.github.com/assets/1521387/1050521/2c2662ea-10bb-11e3-974a-37367dcb0fcf.png)