all: import code from docker fork

This code was originally in the branch remote-api-client of the
repository github.com/fsouza/docker.

There's an open pull request (dotcloud/docker#640) for these changes,
but it will take time to merge this issue, and we need a client for the
Docker remote API in tsuru (see globocom/tsuru#440).
license: add file (BSD 3)
all: add license banner to source files