Added offset/source methods to NodeInterface (#6)
Added offset/length capturing to the lexer and tokens.
Improvement to lexer internals.
Added tests for AbstractNode.
Implement source-capture.
Added source capture to ListParser.
Renamed AbstractPolyadicOperator to AbstractPolyadicExpression
Merge branch 'feature/source-capture' into develop (fixes #6)
Removed redundant implements clause from polyadic operator.