Fix docker images

[werwolfby]

Docker example doesn't work for me. Transmission reject OPTIONS requests if I specify full path to transmission. And --link option doesn't make any sense right now. Because this link is not used (or at least I didn't find usages).

I've updated lighttpd.conf to support proxying. And by default when container just start it will proxying all requests to /transmission/* to http://transmission:9091/transmission/*. This allow me to run docker as it is described in README:

docker run -d --restart=always -p 9092:80 --name cumbustion --link transmission cumbustion

And because of link it can proxying requests.

If name of transmission is not equal to transmission we can specify alias:

docker run -d --restart=always -p 9092:80 --name cumbustion 
  --link some_different_transmission_container_name:transmission cumbustion

It use 9091 port by default, but it can be changed as well by environment variable PORT:

docker run -d --restart=always -p 9092:80 --name cumbustion --link transmission --env PORT=9093 cumbustion

P.S. I've created 2 images and pushed them to docker hub:
https://hub.docker.com/r/werwolfby/alpine-combustion/ - for x86 version
https://hub.docker.com/r/werwolfby/arm32v6-alpine-cumbustion/ - for ARM version
This images can be removed after automatic build implementation