Plugged UPnP Port Mapping.
if the gateway is not UPNP compatible, then we should not do sys.exit, but keep on going without UPnP
s/camelCase_methods/underscoring_methods/ re: #180; SESE style code refactor. Should address issue reported by @SamPatt (Thanks a lot) https://gist.github.com/SamPatt/c7bc3696b8ff7383c6f9
Merge branch 'master' into upnp-portmapping
Merge pull request #179 from OpenBazaar/upnp-portmapping

Plugged UPnP Port Mapping.