expanded test program
added tuple operator
almost done adding let forms to the language, made sure to throw exceptions in most places
started to add proper errors
added source character and line numbers to tokenizer
reverted bug
more error stuff
changed error messages
changed error messages
added another new syntax error
added more error handling, fixed a typo in the tokenizer
added more error checking
expanded test file
more error handling shit
quick update
removed some old comments
basic support for let/def forms in the parser
fixed error handling for let/def
desugaring for let/def expressions, more error handling, expanded test cases
preliminary support for user-defined operators