Using ng2-mobx's wrappers for observable and computed for AoT

Fix lint errors

Fix ng2-mobx version

Fixed release date

Merge branch 'master' of github.com:500tech/angular2-tree-component

Update tsconfig / package.json

Added UMD bundle

Merge branch 'master' of github.com:500tech/angular2-tree-component

version

Allow drag to empty tree

Merge branch 'master' of github.com:500tech/angular2-tree-component