Added basic ie8 support

[bencooling]

Added basic support for deltaY and deltaX values for ie8, bringing it inline with ie9. Tested on Mac with Browsers: Chrome 27, Firefox 21, Safari 6 & a Windows 7 VM running ie8, ie9.

[bencooling]

Please note my fix only supports vertical scrolling. ie8 & less doesn't seem to register the xaxis scrolling event. See: http://stackoverflow.com/questions/10821985/detecting-mousewheel-on-the-x-axis-left-and-right-with-javascript

[blueprintmrk]

try http://www.browserstack.com/ for testing most Browsers

[brandonaaron]

The idea was that if the browser didn't support reporting the event on a different axis, then it wouldn't update those values. Seems as though I should go back to the previous logic of always setting deltaY even if the browser doesn't report a deltaY.

[brandonaaron]

Closing in favor of #74.