test(ticker,trader,balance): tests created; mocha replaces tap

* added test coverage for Bitstamp plugin,
* tap replaced with mocha,
* `mockConfig.json` file with valid (and confirmed) Bitstamp credentials and $5 available for trading on account required to successfully run **all** tests.

This should read like a sentence:

```it('should read the ticker in EUR', function (done) {```