Add edit in place to home page

Fixes #340 

![screen shot 2014-02-27 at 11 48 53 pm](https://f.cloud.github.com/assets/96776/2291976/d53ef31c-a04c-11e3-94da-a9fed774f8d9.png)


Give home page explicit title of "Exhibit Home"
Remove the `#title_or_default` method
Disable "Save changes" button when there are no page **only** on about pages (since you can always save changes to the home page now).

Fix javascript tests that are failing in master due to `pages#update` redirect change.