Replace jQuery.browser

The jQuery.browser() method has been deprecated since jQuery 1.3 and is removed in 1.9.

Old IEs are now targeted via the conditional classes »oldie« or »lt-ie9« added to the html element. This has do be done via conditional comments like the following.

    <!DOCTYPE html>
    <!--[if lt IE 7]>      <html class="no-js lt-ie9 lt-ie8 lt-ie7"> <![endif]-->
    <!--[if IE 7]>         <html class="no-js lt-ie9 lt-ie8"> <![endif]-->
    <!--[if IE 8]>         <html class="no-js lt-ie9"> <![endif]-->
    <!--[if gt IE 8]><!--> <html class="no-js"> <!--<![endif]-->

See [HTML5 Boilerplate](http://html5boilerplate.com) for details to this technique.

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I also updated the README and the demo page.

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This closes #76