- `npm install` will break badly for any submodule being built from scratch as JISON would be missing the lib/util/* files in the repository; I do realize these are 'generated' but they must be included in the repository anyway as a way to 'bootstrap' your own jison build process.

- add `make submodules` make target to speed up the development cycle when you're building jison itself from scratch / working on jison.