The Dockerfile is now stored in contrib and built using the Docker
Hub. This allows us to simply pull in the finished image from the hub
instead of having to build it ourself. Should shave off about 2
minutes from the build time.
I also switched to running the individual build and check steps in
their own containers, but on the same volume, so travis can group the
commands and run them independently.
We intend to ultimately no longer use the legacy `daemon/lightningd`
and instead use `lightningd/lightningd`, so I grouped the new RPC and
the legacy RPC and implemented stubs for the new daemon.
Rusty Russell
Christian Decker