Comprehensive HTTP Router

Here is a partial solution to Issue #202, at least for different HTTP methods.  There is no provision for websocket or SSE support here.  This is more or less a port of the excellent Vert.x RouteMatcher for RxNetty.  I do want to point out that I had to force queryParameters to be mutable on HttpRequest for this particular implementation.
Doesn't the close call at the bottom of the method return an Observable?  I don't understand RxNetty well enough to understand the difference between the Observable returned by `handle()` and the Observable returned by `close()`.  Hopefully you can help illuminate the difference.