add phabricator client (arcanist)

We're going to experiment with phabricator, so
we need the client. It depends on php.
reorg tests into unit and functional

unit tests run first, then functional tests.
fail early on version mismatch between Docker and docker-api gem

* Show docker version at beginning of wercker job
* Check if docker-api gem matches docker version before we
  build the docker image
restrict docker-api gem to be compatible with wercker image

wercker currently uses docker version 0.11.1, which
is incompatible with the newly-release docker-api gem 1.13.0.
refactor functional tests to use ssh, not docker run

If we start a container before the test suite, then
individual rspec examples can just ssh into the container
instead of starting and stopping containers repeatedly.
make test scripts compatible with ubuntu
add functional test for arcanist bash autocomplete
Merge branch 'arcanist'