CMakeLists: Use aux_source_directory() instead of manually adding source files

Advantages:
 - No need to always manually update CMakeList.txt when sources files
   are added/removed.
 - Don't have to send a pull request every time I just fucking added
   source files to CMakeLists.txt

Caveat:

One has to rerun CMake every time a source file is added or removed.
Merge branch 'master' of github.com:crumblingstatue/NoLifeStory