Slow but steady progress
Project parts 1-3 are working
Updated .gitignore

Added back necessary files
Adding in important files
Added an explicit constructor exception to linting

Modified the `make lint` target to include an exception for marking all
constructors as explicit. There is a need for a non-explicit constructor in
this project, and so the change had to be made.
Added section indicators for tests/main.cpp

Added comments indicating the test groupings in tests/main.cpp
Sundry minor testing updates