Wikigrok UX changes

Checkbox buttons:
Add margins around them.

Footer:
* Remove unused button group class
* Address base line of tell me more button

Change-Id: Ib6c9974013ebceae15f27e202189a7354e22aed5

Add margins around checkboxes when together

Change-Id: I6273ce15d7e6425e89fb5a1122b7f179a00b09d9
Merge "Wikigrok UX changes"