Fixing doOnce lang tests
Improving string parsing
Strings can use single or double quotes
better support for comments
Getting image diff tests to actually run
Neateinging up testsSource
Removing unnecessary macro from grammar
Fixing a bug with comments at the end of the program
Cleaning up runner a bit
Merge pull request #242 from rumblesan/grammar-cleanup

Grammar cleanup
Merge pull request #243 from rumblesan/fixing-diff-tests

Getting image diff tests to actually run