Version 2.0

Hey, guys!

The new version 2.0 is upcoming with less limits and more features. Along with few small api changes.

__Highlights:__

* The root node is not required, you can create as many root nodes as you want.
* You can create as many nodes as you want within a request without being afraid that something brakes.
* Few new features, please read [a changelog](https://github.com/lazychaser/laravel4-nestedset/blob/develop/CHANGELOG.markdown).

The new release will have few incompatibilities, please read [upgrade guide](https://github.com/lazychaser/laravel4-nestedset/blob/develop/UPGRADE.markdown).

- [x] Refactor `Node` and `QueryBuilder`
- [x] Refactor `NestedSet` class
- [x] Allow to create nodes from array
- [x] Rewrite README
- [x] Test on NestedSet App