Feature analyticsjstest

This gives us a basic structure to test our JavaScript code.

To do so, some simple steps:

* Create a Test file. If I test `Charts.js` I should create `tests/ChartsTest.js` ;
* Edit `tests/QUnitRunner.html` and call the script to test and the test file ;
* To execute your tests, load the *html* page in your browser.

Here remains some weird results and failing tests about `Charts.js`. Help is welcome, please contact @jlebloas .

After merge, please always unit-test your JavaScript code and try to use TDD !