Add tests

Add mocha and should.js; Add a test; Adjust the grunt and the files accordingly.
The common library would have its own tests. It might use `mocha` or not.
As these might differ, it's cleaner to have the `mocha` definitions here, in the upper repo. Or, have a repo for common test setup, which will be added as a submodule to each 'consumer' `test` folder.