#4569 - package.json update - request ~2.39.0 for fixing a proxy issues

Needs request ~2.39.0 in order to fix a proxy issue with npm, this is due to tunnel-agent and a bad interface problem (0.30.0 and 0.31.0 no revision increased but interface changed).

So, request does not work when a proxy is required with version 2.30.0, npm requires 2.39.0

eg. npm --proxy http://my.proxy.com:8080 update --production