GeneratorManager test - async_done added to ctor options arg
GM - non async impl that calls async_done on completion
JsonCreator, VersionFileWriter tests - added async_done stub to GM configs used (I SHOULD REALLY BE USING MOCK OBJECTS HERE)
grunt_version_file.js - pass done() method in to GeneratorManager at construction
Gruntfile.js - explanation of how to update coveralls.io coverage reports