MaxListenersExceedsWarning when used with http2

I am aware of #7 which was closed a while ago now. However the issue still is occurring for me, using node 7.10.0. I think that is probably because I am using the http2 as the server and because the app that it is serving is a polymer custom components one, so calling index.html does cause an immediate request for quite a large number of additional files (approx 40 if I remember correctly) which should be being served through serve-static.

I have put a trace on the warning and confirmed it comes from the `on-finished` module as expressed in #7. I have also puts some instrumentation in the module that is adding and removing the listeners, so I am pretty sure that although a lot are added they are all eventually removed again, to I don't think there is an actual memory leak happening.

I report it here to see if there is anything that serve static could do to prevent the warning occuring