refactor mojito.js to use yui thru require instead of using the sandbox to avoid posible implications of the sandboxing routine. readjusting the tests to avoid registration of yui modules that can affect other tests down the road.
making sure that the YUI object produced by sandbox has all the proper configuration. in this case Y.config.global cannot be computed from within the vm, so we need to set it manually.
json stringify hack is not needed anymore after upgrading to yui@3.9.1
Merge pull request #1062 from caridy/sandbox-fix

fixes the issue with Y.config.global after the upgrade to yui@3.9.1