Fixed zoom detection for webkit(desktop) and Issue #41

[bitjoo]

I have tested my webkit patch in the latest chromium 28. And on Windows Chrome 27.
Worked with devtools on the right side, activated sidbar and in iframes as well.

I have also fixed the uncaught type exception bug (#41).

[tombigel]

@BitWire cool, thanks!
I'll play with it a bit and merge and change the documentation accordingly this week.

[timbarlotta]

Manually applied the patch and ran some basic tests (chrome 30 on mac) and seems to work great. Did you find issues or any thoughts on officially merging?

[bitjoo]

Because document.width was deprecated and is now undefined in Chrome 30, I made some changes to my code and using the opera detection for webkit now.
Tested in Chromium Version 30.0.1599.114 Built on Ubuntu 13.04, running on LinuxMint 15 (30.0.1599.114-0ubuntu0.13.04.2)

Please have a look.

[nhodges]

@BitWire Doesn't look like your latest pull request is working anymore. Might it be possible to use window.devicePixelRatio now, which has been implemented in Chrome since v31?

Cheers!

[bitjoo]

@nhodges Thank you for your hint. Yes, you can use window.devicePixelRatio. Since Chrome 31 it takes full-page zoom, but not pinch zoom, into account. To get sure, I added a solution with a SVG (iframes not supported). I had to change the browser detection as well, because in Chrome 31 they removed support for the prefixed -webkit-marquee.

If you want to support only the latest browsers for full-page zoom, you can get rid of this plugin and just use window.devicePixelRatio (since Firefox 18, Chrome 31 and IE11, it has the same behaviour).