Created global addListener. Fixed event issue in TreeRunner.
Cleaned up TreeRunner and fixed an IE8 postMessage-related issue.
Updated documentation.
Merge pull request #290 from gvsboy/master

fix(TreeRunner): fixes listeners for IE comaptibility

Internet Explorer needs a special addListener method since attachEvent isn't always
available. This adds a common add/remove listener function to the globals, which is
used in both the main Inject file as well as the nextTick function. In addition, some
cleanup was done in the TreeRunner file to improve readability.