Update some API references that had fallen out of use.
Notably this no longer ran, since docker.#Run now asks for an "input" not an "image," alpine.#Image became alpine.#Build and you have to reference its output.
Remove a FIXME -- now copies the inline script to the container as a file rather than executing it with python -c.
Add tests
Signed-off-by: Adam Smith <adamsmith@nottheeconomist.com>
* `cmd` is renamed to `command` for readability
* `script` is removed. Feature moves up the stack (bash.#Run,
python.#Run)
Signed-off-by: Solomon Hykes <solomon@dagger.io>
