Give credit where credit is due

examples/ExternalGravity/makeIC.py

examples/TestingGravity/makeIC.py

examples/main.c

src/cell.c

src/cell.h

src/const.h

src/engine.c

src/engine.h

src/gravity/Default/gravity.h

src/runner.c

src/runner.h

src/space.c

src/space.h

src/task.c

src/task.h

src/timers.c

src/timers.h