Package Expansion for testing commands

This adds package expansion to the testing commands: ``funittest``, ``ffunctionaltest``, and ``fbehattest``. For a description of package expansion see cognifloyd@d160362d67f111982f2af099b357a302d85b52b6.

This pr is based on #4. This patch includes everything in the [cognifloyd@expansion branch](https://github.com/cognifloyd/oh-my-zsh-flow3-plugin/tree/expansion) as well as the behat command in sandstorm@c03a89bb8d0c363a795312470d691de2ea5ee774, and then adds package expansion to the behat command in cognifloyd@cf6b4e0ba533418b4c71629df1b714f7a171efdb.