Improved the PathLexerInterface so that it requires the get/setParameter functions.
Fixed a bug in the query string lexer where null was not treated as the end of a parameter.
Fixed a typo in the path lexer.
Added examples to the readme showing how to use the lexer classes.
Complete testing and bugfixing of query expressions.
Complete testing and bugfixing of path expressions.
Complete testing and bugfixing of variable expressions.
Complete testing and bugfixing.