build: bump devmode diamond version

... to latest, because the older version didn't
correctly detect virtualenvs and that broke installation
inside travis.  Note that this is just the version of diamond
used by the minion-sim, nothing to do with what we install
on ceph clusters.

Signed-off-by: John Spray <john.spray@redhat.com>
build: use libzmq3 instead of libzmq in devmode

The libzmq1 package in travis happens to be broken,
and it does us no harm to have a more recent one.

Signed-off-by: John Spray <john.spray@redhat.com>
build: create .travis.yml

This is the configuration file that allows
travis-ci.org to run on our repo.

Signed-off-by: John Spray <john.spray@redhat.com>
doc: Link travis build status in README

Signed-off-by: John Spray <john.spray@redhat.com>