Write unit tests for include/epesi.js.

Wrote some unit tests, starting with the include/epesi.js file. Chose a JS unit testing framework (flipped a coin). Got tests passing, but there are some issues. Commit summary below:

* Use QUnit testing framework.
* Add tests for include/epesi.js.
 * These tests are really difficult to write and brittle. The file needs some serious refactoring to make life better.
 * Tests for js loader and css loader functionality required too much effort to write at present. Skipped for now.
 * Cannot test browser detection across browsers. That test is rather hacked.
* In include/epesi.js, getTotalTopOffet ==> getTotalTopOffset
 * This method doesn't seem to appear anywhere else. Can it be deprecated/removed?