Move all the example code to its own repo

[sheenobu]

This will help remove cgo and SDL2 dependencies when pulling the library.

[dmitshur]

when pulling the library.

If a user does go get -u github.com/sheenobu/go-obj/obj, they will only get that package and its dependencies (recursively). The only external dependency is github.com/pkg/errors. See https://godoc.org/github.com/sheenobu/go-obj/obj?import-graph&hide=2.

If a user does go get -u github.com/sheenobu/go-obj/cmd/obj-renderer, only then will it fetch all the SDL/GL/etc. dependencies, as seen at https://godoc.org/github.com/sheenobu/go-obj/cmd/obj-renderer?import-graph&hide=2.

[sheenobu]

That's good to know, thanks. I'll update the README. I would still like to move the example code elsewhere. Currently depends on libraries which don't exist outside of the vendor/ folder.