Fix error reporting for one_or_more rule

Right now if we parse wrong PEG grammar we got this

```
Unexpected "s" expected (EOF)
1: GRAMMAR test a -> "A"; should_fail -> "B" -
--------------------------^
```

We should get more informative error message, like this

```
Unexpected "-" expected (;)
1: GRAMMAR test a -> "A"; should_fail -> "B" -
---------------------------------------------^ 
```
