Update babel-standalone to latest version

[codewithmichael]

The babel-standalone project was updated to version 6.10.3 to match the Babel version. It would be preferable to stay up-to-date with them.

Unfortunately, version 6.10.3 includes a conflicting feature (babel/babel-standalone#15) whereby it parses <script type="text/babel"> tags on DOMContentLoaded.

This can be hacked around by temporarily intercepting window.addEventListener(), but this kind of hack is fragile and bound to break with a future release.

I have put in a feature request for a method to remove the event listener (babel/babel-standalone#39).