remember input string in result

parser.go

@@ -80,7 +80,7 @@ func Run(parser Parserish, input string, ws ...VoidParser) (result interface{},
 		ps.WS = ws[0]
 	}
 
-	ret := Result{}
+	ret := Result{Input: input}
 	p(ps, &ret)
 	ps.WS(ps)
 

result.go

@@ -15,6 +15,7 @@ type Result struct {
 	Token  string
 	Child  []Result
 	Result interface{}
+	Input  string
 	Start  int
 	End    int
 }