Updated to correctly handle errors from Meteor

The getMeteorVersion method would both return and emit errors if the
Meteor --version command failed. It will now only return the error
(since the event wasn't handled anyway) and the error has been updated
to reflect the problem.

Includes a test case for this scenario.

Closes #76.
Merge pull request #77 from onmodulus/bug/error-with-no-meteor

Updated to correctly handle errors from Meteor