clean up and bug fixes
ignore build by products
IntervalSet.complement implementation

implementation of complement, test case, and usage
documentation edits
fix character processing in error messages
SingletonPredictionContext .to_s simplification

improve the performance of .to_s based on -Xprofile output
fix escaping of whitespace in error messages
speed up == for ATNConfig
range needs a/b to work with IntervalSet
future features for intervalset
Predicates have a length but not each.

use lenght to drive looping over the Predicates
transition.label: encodes transition as IntervalSet.

it is not an attr accessor
def label needs to exist and is not an accessor as I first assumed.