Added a GoKitLiteActions class for custom tween actions

Added GoKitLiteActions class which currently contains a few custom
actions
to do position and localScale shaking of transforms.

GoKitLiteActions.cs: New file for custom actions
SimpleTweenUI.cs: Updated to show examples of using some the
GoKitLiteActions
README.md: Added a section on the GoKitLiteActions class