* Build docker image of nomulus tool
In the course of "gradle build", build a docker image of nomulus tool so that
users can run this to allow us to bundle the java version with the image.
* Remove the maybeRuntime configuration
It contains dependencies present in the bazel
build but not needed for compile. We now know
they are not needed in runtime either.
This PR prevents Gradle from copying the golden images
to build/resources/test, so the screenshot test would
read golden images from src/test/resources directly and
display the path in test log if the test fails. Because
the path pointing to the actual file in src/ folder,
the engineer can easily find it.
Our CI (Travis & Kokoro) runs "gradle build", so we need to make
sure that all tasks used in the release process are called during
the build so that breakage can be caught earlier.
In order to stage the GAE folder we need gcloud to be present.
Therefore the Travis config is changed to install gcloud.
See: https://gist.github.com/mjackson/5887963e7d8b8fb0615416c510ae8857
