Update RoboActionBarActivity.java

Changing onContentChanged() to onSupportContentChanged().

This fixes https://github.com/metova/roboguice-appcompat/issues/2.

This repo should be deprecated soon.  Once RoboGuice 3.0 comes out this class will be provided (see https://github.com/roboguice/roboguice/blob/master/roboguice/src/main/java/roboguice/activity/RoboActionBarActivity.java).