Set up test runner and change test folder structure

Created by: AxelDelmas

• run tests with npm test
• use npm run debug to run test with iron-mocha (test run in chrome's devTool)
• use npm run coverage to run tests with istanbul

Several things to clear out:

• I implemented these as npm scripts, as I found this more straightforward (They can still be integrated as is into grunt workflow using grunt-shell for example). Do we want to change these as grunt tasks, or keep them as npm script? I'll need to clean the Gruntfile and package.json when this is decided.
• Is there a reason const is use everywhere in the "dash" unit tests? I find this confusing to use it with reference types, as the variable can't be reassigned, but the object itself can be modified (it is not immutable). I can modify that if that's ok.
• I fixed some paths in my first commit, but as all folders are lowercase, it might be better to rename the folders instead of the paths.
• I removed some unused imports (in isolated commits). Please review this and tell me if they actually had a purpose.