Regenerate docker image on top of latest upstream

[mboes]

The haskellr docker image builds on top of the stock images provided by the stack project. They recently changed the entrypoint (see #202) so that entering the image is more efficient than it previously was. We should regenerate our docker image on top.

@borsboom I foresee the docker registry caching getting in the way. Do the new images with the fixed entrypoints have a different tag associated to them?

[borsboom]

@mboes Every image we upload to the fpco repos gets its own unique tag. Note that only the LTS-3 images have the fixed entrypoint.

[mboes]

Fixed by #218.