Adjusted OnScrollAttribute and OnScrollStateChangedAttribute; added unit tests.

Hi JiHun,

It seems Robolectric has not implemented AbsListView.OnScrollListener related support. I posted a question into their google group - https://groups.google.com/forum/#!topic/robolectric/RI5LS-naJOU. And I have tried with the latest version Robolectric 2.3, which does not seem to work. I think we place @ignore annotation on unit tests for now and once the OnScrollListener gets supported, we can enable them.

In the pull request, i removed some unused classes and did some minor changes. Please have a look. If you think the changes are ok, you can update your RoboBinding to the latest and transfer these changes over and submit your pull request again. We are looking forward to your contribution in future.

Best regards,
Cheng Wei