Slight tweaking

[beelsebob]

Hi Gavin,

I just thought I'd let you know that I've updated CoreParse a little to support rather cleaner access to the elements of a rule, the example in the readme now uses them. This allows you to tag rules as follows:

Expression ::= term@<Term> | expr@<Expression> op@<AddOp> term@<Term>

And then in the implementation of initWithSyntaxTree: allows you to get at these tagged sections easily by using [syntaxTree valueForTag:@"term"]