IE9 needs overflow: hidden style on <svg> element

[smithclay]

Noticed an odd issue in IE9 where sometimes the content in the svg element overflows the bounds of the svg element in IE9, which doesn't seem to be the behavior in other browsers.

Adding the inline style="overflow: hidden" to the svg element seems to fix the problem, though. Here's a related discussion that also talks about the issue:

http://stackoverflow.com/questions/5971320/svg-image-is-not-cropped-in-ie9
simplegeo/polymaps#9

[dchester]

I think this should have been fixed with 4bb1985. Let me know if you find otherwise.