Added more documentation to readme.md
Changed yyparse to yyparse(TopNode**, yyscan_t)
Implemented ParserTopNode.c
Added ParserReturnType enum for ParserTopNode
Verified that ExpressionNode can have a union
Added "pass" keyword, function definition, variable definitions
Added "todos" file to better keep track of todo's.
Added method stubs for TypeSystem.h ; will implement later.