start translation of Python combinators
finish transcribing Python combinators
get majority of tests passing; fix small translation errors in combinators
ignore project files
get tests running for position and count Itemizer parsers
translate cst module and test; remove junk example
add tests for oneOf combinators (and fix problem in implementation)
some combinator fixes:

 - `optional` -- use `null` as the default value (if one isn't supplied) instead of `undefined`, to explicitly show the value in the result. update tests accordingly

 - fix silly mistake in `Itemizer` -- accessing instance's combinators in certain ways would result in the desired `this` not being used.  Fix by creating functions in an inner function scope so that they properly mutually refer (without need for `this`)
start json parser example and tests
make argument order for test cases consistent: actual, expected
finish CST tests for JSON example parser
improve parameter names
change function order so that if y depends on x, y comes after x