Avoid duplicating warning in ng-repeat

[rhcad]

1. Add " '~' + $index" in the following line:

   <li ng-repeat = "row in tree_rows | filter...track by row.branch.uid || '~' + $index">

   When row.branch.uid is empty, ng-repeat error will occur: "Duplicates in a repeater are not allowed".

2. Fix the variables of the example in README.

   <abn-tree tree-data = "my_treedata" ...>

   $scope.my_treedata = [{ // Replace 'my_data' with 'my_treedata'
     label: 'Languages',
     children: ['Jade','Less','Coffeescript']
   }]

3. Add repository and fix license in package.son (licence -> license).

[daerogami]

uid should never be empty so I'm not sure if this change is necessary; however, the other cleanup items are still valid.