Work in progress orbital shipping game

Dependencies:
	libTangerine: https://gitlab.com/cinnaboot/tangerine
	Catch2 (for tests):
		https://github.com/catchorg/Catch2/blob/devel/docs/Readme.md

TODO:
	add GUI to demo application for modifying orbit parameters
	add equations for parabolic and hyperbolic trajectories
	make algorithm for Hohmann transfer orbits
	you know, make the actual game

Building:
	install dependencies for your environment:
		Arch) $ sudo pacman -S assimp glew glm sdl2 catch2 gcc make
		Fedora) $ sudo dnf install assimp-devel glew-devel glm-devel \
			SDL2-devel catch-devel gcc-c++ make
	checkout, and initialise submodule dependencies:
		$ git submodule update --init --recursive
	build:
		$ make

	binaries will be in ./bin

	NOTE: if you get errors regarding assimp when building, you can build a
		recent version of assimp with the instructions here:
		https://gitlab.com/cinnaboot/tangerine

		For example after doing the git submodule commands above do:

		$ cd ext/tangerine
		$ make build_assimp && USE_INTERNAL_ASSIMP=y make

		then, to run the demo,

		$ cd ../../bin
		$ LD_LIBRARY_PATH=../ext/tangerine/ext/assimp/lib ./orbital_shipping