Added Lexer

Signed-off-by: Stefan Marr <git@stefan-marr.de>
Added method to get the name of an int representing a symbol

Signed-off-by: Stefan Marr <git@stefan-marr.de>
Use Python file objects directly as input

- fix wrong separator between path and filename

Signed-off-by: Stefan Marr <git@stefan-marr.de>