Added new Collection for Baum/Node.php
Added a new Baum/Collection.php method toHierarchical()
update dependencies for laravel 4.1 (supporting 4.0)
Make travis test against php 5.5.
Merge branch 'master' of git://github.com/Surt/baum into flat-to-hierarchy

Conflicts:
	src/Baum/Node.php
Add a simple test case for 'toHierarchy' method.
Change impl a lil (lil) bit to properly set model relationships & clarity. Also, make custom Collection object as transparent as possible.
Merge branch 'flat-to-hierarchy' into develop