Implemented the following attributes:

* String.length
* String.asUpper
* String.asLower
* array.length
* array.pushBack(x)
* array.popBack()

The remaining attributes are listed in 'toy_attributes.h'

source/toy_parser.c

@@ -751,7 +751,7 @@ static Toy_AstFlag attribute(Toy_Bucket** bucketHandle, Toy_Parser* parser, Toy_
 		}
 
 		Toy_private_emitAstAttribute(bucketHandle, rootHandle, expr->varAccess.child);
-		return TOY_AST_FLAG_NONE;
+		return TOY_AST_FLAG_ATTRIBUTE;
 	}
 	else {
 		printError(parser, parser->previous, "Unexpected token passed to attribute precedence rule");