Adds support for dynamically loading the polyfill by setting up 0 times if the document is already loaded at the time the polyfill script is processed.
This is done by checking document.readyState == 'complete'.
Add warning for dynamic loading in the absence of performance timing. In this case, document zero time is incorrect.
Warn the user about document zero time only if the polyfill is loaded dynamically and performance timing is unavailable.
Merge pull request #129 from sorvell/master

Add support for dynamically loading polyfill (after document has loaded).