In the pipeline design, several beam commands can be run concurrently,
with their respective inputs and outputs connected in such a way that
beam messages flow from the first to last. This is similar to the way
a unix shell executes commands in a pipeline: instead of STDIN and
STDOUT, each beam command has a "BEAMIN" and "BEAMOUT".
Since beam allows for richer communication than plain byte streams, beam
pipelines can express more powerful computation, while retaining the
fundamental elegance and ease of use of unix-style composition.
Docker-DCO-1.1-Signed-off-by: Solomon Hykes <solomon@docker.com> (github: shykes)