Specify main class for helios-tools:CliMain

So that we can run it with `java -jar`
and make this guy happy:
https://github.com/Homebrew/homebrew/pull/33656#discussion_r19542779
Upgrade docker-client dependency

-RN

* This new docker client adds SSL/TLS support for Helios to Docker
  communications.
* The DockerCertificates class can now be used to build an SSL context for
  communicating with Docker over HTTPS with client/server authentication.
* Note that we ignore hostnames when verifying SSL certificates. Instead,
  we just make sure that the certificate is from the correct CA. Hostname
  verification is pointless here since everyone is just using self-signed
  certs anyway.
* The way we test this stuff is a bit interesting too: we start a
  container and run an HTTPS Docker instance inside the container,
  and see if we can connect to that with the appropriate certificates.

* Don't send requests to start a container to Docker using chunked
  encoding.
* This is to workaround a bug present in Docker 1.2.0, wherein the
  HostConfig is completely ignored if sent with chunked encoding.
* To enable testing this, we add ContainerInfo.hostConfig(), which returns
  the HostConfig we get from inspecting the container.
Default to Unix socket on Linux machines

On Linux machines, default to unix:///var/run/docker.sock to talk to Docker
instead of HTTP. This will help Helios work right out of the box on Linux
boxes.
Merge pull request #228 from spotify/rohan/unix

Default to Unix socket on Linux machines
Honor env vars when using builder

Previously, we would honor HELIOS_DOMAIN and HELIOS_ENDPOINTS
only if the caller used TemporaryJobs.create(). We now honor
those variables even if the caller uses the builder directly.
They can then override those values with hardcoded ones using
builder methods.

-RN
TemporaryJobs builder object now honors HELIOS_DOMAIN and
HELIOS_ENPOINTS.Previously they were honored only if the
caller used TemporaryJobs.create().
Merge pull request #248 from spotify/rculbertson/temp-jobs-create

Honor env vars when using builder
Don't paralellize VersionResponseFilterTest

Tests that inherit from SystemTestBase should not be run parallelized,
since completion or an exception in a single test method will trigger a
teardwon of the Docker client and connection pool. All remaining tests
will then fail.
Merge pull request #250 from spotify/rohan/fix-test

Don't paralellize VersionResponseFilterTest
CircleCI: Collect Docker logs as an artifact

This can be useful for debugging after failed tests.
Merge pull request #252 from spotify/rohan/circle-log

CircleCI: Collect Docker logs as an artifact
Support connecting to Docker via HTTPS

We will attempt an HTTPS connection if a path to a client.key/client.pem
pair is specified via the --docker-cert-path argument in the agent or via
the DOCKER_CERT_PATH environment variable.
Merge pull request #251 from spotify/rohan/ssl

Support connecting to Docker via HTTPS
Upgrade docker-client dependency