Update method signature in server example

Signed-off-by: Michael Elsdörfer <michael@elsdoerfer.com> (github: miracle2k)
Make server example register with proper port syntax.

Before, you needed to specify the port without a colon and the
service was registered in the same way.

Signed-off-by: Michael Elsdörfer <michael@elsdoerfer.com> (github: miracle2k)
Add Procfile, for easy development env setup.

Signed-off-by: Michael Elsdörfer <michael@elsdoerfer.com> (github: miracle2k)