Adapter for Nom

[m4rw3r]

Feature which enables an adapter-function to call out to a Nom parser.

impl<'a, I: 'a> Input<'a, I> {
    // ...
    fn nom_parser<T, E, F>(self, F) -> ParseResult<'a, I, T, E>
      where F: FnOnce(&'a [I]) -> nom::IResult<&'a [I], T, E>;
}

Use a closure if extra parameters need to be passed to the Nom parser.

Also needs to support an error type allowing for both Nom's Err type as well as Chomp's parsers::Error.