Add mocha tests

[stephenlacy]

Currently the plugin has no actual tests. The Travis builds are passing because they are getting a status code of 0.

An example of correct Mocha testing would be: https://github.com/stevelacy/gulp-bump/tree/master/test

[karimsa]

Thank you for that, I've actually been working on the tests. They'll be up soon.

[karimsa]

Just a future note, currently this package is labeled as version 0.1 under the npm registry. This is incorrect as the package available on npm is 0.0.9 and version 0.1 is the version with the first push of tests. So when I push the tests, the real version 0.1 is the one with the 0.1.0 tag on GitHub.

[fidian]

Version 0.1.1 was pushed 2 days ago and there are still no tests. Are there even some partial tests coming in the near future? I am greatly looking forward to them! :-)