Switch to a multistage build for the container image (#225)
Switch to a multistage build for the container image (#225)

This makes it easier to reason about tusd's run environment. It also
significantly lowers the docker image size from 280MB for the current 0.11.0
image to only 26MB. Also not having the entire build environment in the
shipped images makes it quite attractive to use this image as a base
for other images. Those could contain some custom hooks for example.
tus/tusd,tus/tusd