Tag releases

[bjarketrux]

Would it be possible to create official releases based on gliderlabs/logspout releases?
That would be tags in this github repo and tags in https://hub.docker.com/r/bekt/logspout-logstash/tags/

Then we could use the official releases instead of master or latest, e.g.:
docker pull bekt/logspout-logstash:v3.2.5

This will give us the possibility to roll back and also to use official releases instead of last commit.
Thanks

[Bekt]

Hey @bjarketrux ! I put something quick here in #8