Migrated to gradle
Save and restore view instance state
Delete PullToRefresh ListView
Fix not restored exact item position which next to first item
fix NullPointerException
add content background colour
Merge branch 'view_instance_state' into master_gdg

* view_instance_state:
  Fix not restored exact item position which next to first item
  Delete PullToRefresh ListView
  Save and restore view instance state