Add Logging

[carlschroedl]

Choose a library for logging, and sprinkle a few appropriately-leveled log statements in a few classes. Strong preference is given to a library that implements the PSR-3 Logging Interface.

At least two candidates: Monolog KLogger

If the pivot web app backend already uses a PSR-3-compliant Logging Library, then that should be used.

[andrewshell]

Laravel which is what we're using for the API uses Monolog. We can implement PSR-3 in this library without depending on a specific library. Although we can choose one as a dev dependency if we want to have logging in test scripts.