universe: python: Update to 0.2

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>

pkg/universe.dagger.io/python/test/data/helloworld.py

@@ -0,0 +1,2 @@
+with open('out.txt', 'w') as f:
+    f.write("Hello, world\n")