Added YUI library to the repo

Fixes #792

The tests now run for this app :-)

ITs-MacBook-Air:browser-tests ceberhardt$ mocha allTests.js  -R spec --framework=yui


    TodoMVC - yui (1/1)
    No Todos
      ✓ should hide #main and #footer (199ms)
    New Todo
      ✓ should allow me to add todo items (579ms)
      ✓ should clear text input field when an item is added (316ms)
      ✓ should trim text input (563ms)
      ✓ should show #main and #footer when items added (409ms)
    Mark all as completed
      ✓ should allow me to mark all items as completed (1091ms)
      ✓ should allow me to clear the completion state of all items (1055ms)
      ✓ complete all checkbox should update state when items are completed / cleared (1283ms)
    Item
      ✓ should allow me to mark items as complete (916ms)
      ✓ should allow me to un-mark items as complete (861ms)
      ✓ should allow me to edit an item (1155ms)
      ✓ should show the remove button on hover 
    Editing
      ✓ should hide other controls when editing (705ms)
      ✓ should save edits on enter (1155ms)
      ✓ should save edits on blur (1214ms)
      ✓ should trim entered text (1124ms)
      ✓ should remove the item if an empty text string was entered (1053ms)
      1) should cancel edits on escape
    Counter
      ✓ should display the current number of todo items (499ms)
    Clear completed button
      ✓ should display the number of completed items (978ms)
      ✓ should remove completed items when clicked (871ms)
      ✓ should be hidden when there are no items that are completed (922ms)
    Persistence
      ✓ should persist its data (2367ms)
    Routing
      ✓ should allow me to display active items (922ms)
      ✓ should allow me to display completed items (859ms)
      ✓ should allow me to display all items (1200ms)
      ✓ should highlight the currently applied filter (1081ms)


    26 passing (2m)
    1 failing