Add JS-Unit Tests for Timelines

Implements [2368](https://www.openproject.org/work_packages/2368)
Basically introduces Mocha as a testing framework for javascript.
Also adds some tests for timelines.
The tests can be run by simply opening mocha/index.html in any browser.
If one wants to run the tests on the command line, [mocha-phantomjs](https://github.com/metaskills/mocha-phantomjs#installation) is required. Just call ```mocha-phantomjs mocha/index.html```