The jQuery team have made the tough, but inevitable decision to stop supporting IE8 and below as of jQuery v2.0, while maintaining v1.9 as the backwards compatible version for the forseeable future.
In the world of modern, evergreen and mobile browsers, this was a necessary move to ensure jQuery stays relevant. Of course, this split leaves plugin authors with a bit more responsibility.
Where previously we could simply require the most recent version of jQuery, we are now likely to want to support both 1.9.x and 2.x, allowing our plugins to work everywhere from IE6 to the most bleeding edge browsers.
Read more: http://markdalgleish.com/2013/01/testing-jquery-plugins-cross-version-with-grunt/