Update to Go v1.3

Now I’m just being OCD about it.

Dockerfile

@@ -2,7 +2,7 @@ FROM ubuntu:12.04
 # Let's install go just like Docker (from source).
 RUN apt-get update -q
 RUN DEBIAN_FRONTEND=noninteractive apt-get install -qy build-essential curl git
-RUN curl -s https://storage.googleapis.com/golang/go1.2.2.src.tar.gz | tar -v -C /usr/local -xz
+RUN curl -s https://storage.googleapis.com/golang/go1.3.src.tar.gz | tar -v -C /usr/local -xz
 RUN cd /usr/local/go/src && ./make.bash --no-clean 2>&1
 ENV PATH /usr/local/go/bin:$PATH
 ADD . /opt/etcd