report unmatched close brace error
report illegal final backslash error ranges
added arg1 TokenException constructor
report unrecognized command error ranges
fixed regression with Macros
updated TODO
added unit tests

caught a regression in \mathbb rendering
added 3 more unit tests
added another unit test
added 2 more unit tests
added another unit test
Merge pull request #3 from mattrajca/master

Fixed regressions, added more unit tests, report more errors