Fix for Google Chrome and Firefox ignore target attributes when opening ...

I was using the examples.phaser.io page in the sideview mode in Chrome and the iframe links were opening in a new tab/window instead of the #viewer iframe as intended by the page. This fix makes sure the link opens in the same page (thus enabling the change of examples without loading a new tab every time).

I did not limit this by user agents but I think it should not impair the ability to load the file in the iframe in other browsers which would not have this problem.

See more information regarding the issue here:
https://code.google.com/p/chromium/issues/detail?id=135498