Update Docker Hub to include ARMv7 images

I tried pulling the container on my RPi 2 and got an error saying it couldn't find an ARMv7 package, even though ARMv7 support was merged in #14. It looks like the version on Docker Hub was last published 7 months ago which predates this PR, so another push to Docker Hub would be great so I don't have to pull/build locally. Thanks!