Only build master branch on travis-ci
Fix two issues:

#1 http.request ignores hostname specified through "hostname" option. Now hostname has priority over host, as per Node documentation.

#2 bufferToString fails when encoding passed is undefined. On real NodeJS this works fine, and some popular NPM modules (request) were breaking in part because of this.

Also add the 'constants' module from Node's sources.
Arrange for the JS code to initially run in an event loop thread, to avoid several different loops being created that could then execute code at the same time.

I also added a check to ensure that .end on an internal http client request is called only once, since NodeJS seems to tolerate that and I've caught npm modules doing it.
Add some fs.WriteStream bits
Remove unnecessary sleep now that top-level is in the event loop
Make Nodyn subclass DynJS. Extend DynJS Runner to always run in an event loop.
Fix package names and run top level script on a vertx context
Make sure we use the right runtime in the repl