Revert "Make quit() and exit() work Issue #36"

This reverts commit cf84bbcb4da0fe4a928de94b35530972db13a285.
Make quit() and exit() work correctly, as builtin functions.
Export QuitException symbol to pass dist test.
Merge branch 'master' of github.com:rixner/skulpt into rixner-master

Conflicts:
	dist/builtin.js
	dist/skulpt.js
	src/builtin.js
	test/run/t479.py
	test/run/t479.py.real
re-add quit to builtin.js
Re-add new test for quit as a builtin function
Rebuild dist.

All tests pass