Beginnings of unit testing
Added CuTest C unit testing library
Pulled in ad-hoc tests
Modified CMakeLists.txt to build test-doom2k (untested, ironically)
Created stub main method; removed old tests.c file
Merge branch 'unittests' of https://github.com/camgunz/d2k into new_data_structures

Conflicts:
	CMakeLists.txt