Go Compiler Version .. second round

The last pull request I made did make the docker build work .... however, after building the logstash forwarder did not compile because of the version of the go compiler Debian provides.

I you check issues such as 
https://github.com/elasticsearch/logstash-forwarder/pull/217
You'll understand (like I did) that for the TLS to work, currently logstash-forwarder NEEDS goland 1.2.x ... however debian does not provide this version anymore ...

So I changed the Dockerfile to download the binary tar.gz of the go 1.2.2 compiler, made a few changes to take this into account and ... there we go ;)

PS : sorry for the useless commits included in this pull request ... It's only my second PR, and well ... I must have failed somewhere ;)