fixed display error and updated variable name aross template and directive which creates the scope
updated toggling and selection algorithm. Update node cost on every execution, which is recursive. Not maximally efficient, but works for now. Addition of a 'dirty' field could reduce number of recursive executions. Minor variable name update
refactored selection so it works with any data type, eliminating the need for multiple handlers
added root function to tree with tests
selection controller now uses tree model instead of node directly
added address function to tree with tests