Add 19 pytest tests covering the report, resource check, coin
processing, refunds, change, profit, make_coffee and the main loop.
Add a tests package and put the project root on the pytest path.
Doxygen output is clean. The repository description and topics were set
on the git host.
Closes#13Closes#14Closes#15Closes#16Closes#17
Task: MIL-003#1
Task: MIL-003#2
Task: MIL-003#3
Task: MIL-003#4
Task: MIL-003#5