WIP - first pass at adding scheme scripting. Functional but slow.

Also, use of scheme vs. a rule file is hardcoded at the moment.
Needs a way to define scheme file to load in data file, or rule file to
load.
Might need to pass the full board to scheme, or register neighbor
counting as a native function for speed.
Might also need to use some forms of cacheing
Makes scheme interface use primitive functions to get/set/count cells
Makes generate() in backend.c call scm_generate correctly
Improves Scheme interface and simplifies the most common pattern
Moves scm helpers to core.scm. Adds board_set_cell() to board.c/h
Put loading of scheme module into rule.c
Added scheme filename/module/function definition to rules file
Removed unused core.scm Scheme module
Made Makefile use glfw3's pkg-config for libs/cflags
Merge branch 'develop' into feature/scheme

Conflicts:
	src/Makefile
Made rule files w/ scheme not need neighbor type or transition data.

Made a run_scm_life.sh for running an automata that uses scheme. Made
run_life use the C-based life rules
Made world global use a _g suffix
Merge pull request #16 from calebsmith/feature/scheme

Adds support for automata rules in Scheme