add alpine image for ghost2

[voigt]

This is based on the ghost-1.0 alpine image.
I had to add line RUN chmod +x /usr/local/bin/docker-entrypoint.sh to make it work - not a docker expert.

Maybe this helps someone to try 2.0 asap (#142 ) :)

Build with
docker build --no-cache -t ghost/ghost:2 .

Run with
docker run -d --name <ender-name> -p 3001:2368 ghost/ghost:2

[tianon]

Thanks for the contribution!

We opted for #145 since it's more complete (and removes relevant bits that are no longer necessary). 👍