Run one travis build with valgrind on legacy tests, off on new daemon
tests, and another build with the roles switched. Should also speed
this up a bit since we run in parallel.
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.
Added .travis.yml to get travis-ci to build and run tests for us.
In addition this fixes a flaky test due to the fact that when lightning2
connects to lightning3 and we tell lightning3 to restart, then
lightning2 will back-off its reconnection attempts, potentially causing
a timeout to trigger during tests. This was triggered by travis-ci
relatively consistently since the restart would take quite some
time. Now simply restarting them in reverse order and a small timeout
seems to fix this consistently.
