Support Local Source Inclusion

[nicholaschiasson]

Currently, car can only compile and run single source file programs. Including or importing files to be compiled into the output is not possible. This change will bring car a step closer to being a more universal source launcher, exceeding its initial intended purpose. That being said, it's still an appetizing feature to have. To do this, it will need to parse files for "include" or "import" lines depending on the type of source file and then try to compile multiple source files into the output.