Durations are Longs not longs as they are optional

The model already treats the Duration as a Long but the parser insitst its a long causing Longs to be unboxed and then re-boxed.
if the duration is missing (as the result is skipped) then this causes a null pointer exception trying to parse the json.
Merge branch 'patch-1' of https://github.com/jtnord/gherkin
Attribution for #276