Remove phantomjs work-around (package.json script)

[stevenjmarsh]

In order to prevent error messages emitted by phantomjs, meteor reset is called before meteor test in several package.json scripts.

Once a fix is indentified for this, either a later version of phantomjs, or a substitute option (like aldeed mentions), update the scripts to run the tests properly, and without the meteor reset.

Information on the issue found with phantomjs.

[stevenjmarsh]

nightmare/electron for headless testing has been suggested in other conversations too.