Update build-tools to 21.1
Added setAbsListView to ExpandableListItemAdapter

Also updated the Exception messages to contain the new
setListViewWrapper method.
Use NineOldAndroids library to make Drag and Drop and the example app to work on API 8 or higher.

Fix running example app on Emulator without Google Play Store.

Fix most problems with drag&drop on API levels < 14.
Also contains fix for #254

refresh mMobileView only when needed.

Fix visible mobileView when dragging on API < 14.

This works only when SimpleSwipeUndo is enabled too. When it's not enabled the mobileView remains is visible.

Some cleanup, fixed scroll item swapping.
Fixed Travis build - do not run tests on CI.
Removed secure elements from .travis.yml to move them to the Environment Variables online.
Merge pull request #284 from WonderCsabo/setAbsListViewInExpandableListItemAdapter

Added setAbsListView to ExpandableListItemAdapter