add unit tests

[basvanbeek]

This project started out as an investigation project to see how to work with the various concepts within Go kit and to see how to properly build the OpenCensus and ocsql middlewares.

Due to the nature of constant refactoring and playing around to find the right way I skipped the step of unit tests given the limited amount of time and me being lazy. It is time to add these to aid with future refactors and fix bugs that are bound to be found.