Remove Google Chrome Frame

Google has discontinued Chrome Frame and prints a console message indicating it no longer prompts.

`Google Chrome Frame is being retired, so the CFInstall.check method no longer notifies the user; see http://blog.chromium.org/2013/06/retiring-chrome-frame.html for more information.`

Fix #1376
Remove comments about IE8-style button mapping.
Merge remote-tracking branch 'origin/master' into remove-chromeframe

Conflicts:
	CHANGES.md
Try harder to get error messages through to old browsers.
Further refinement of WebGL error on old browsers.
Remove most old browser detection by using more compatible code.

* createTextNode instead of textContent
* setAttribute for button type
* querySelector instead of getElementsByClassName
Merge pull request #1618 from AnalyticalGraphicsInc/remove-chromeframe

Remove Google Chrome Frame