JSON to PPM raycaster by Chris Blazer
Use "make" to implement the makefile, which compiles the program using gcc.
Usage is just how the project specified; "raycast width height input.json output.ppm".
Can output to ppm 3 or 6, but project did not specify to put that into command line arguments so it is hardcoded into write_scene() function call in main().
Program will create the output file if it does not exist.