Better Dockerfiles for smaller containers

Cleanup apt after we use it for smaller container size. I also reordered
some of the commands to put the things that change more often nearer the
bottom allowing us to build newer containers faster. Use newer Ubuntu
for newer openssh (no real reason other than newer is better?). These
Dockerfiles were used to produce the 1.2.0 containers on dockerhub.

Author: bobveznat

Dockerfile

@@ -1,9 +1,8 @@
-FROM ubuntu:14.04
+FROM ubuntu:15.10
 MAINTAINER Bob Van Zant <bob@veznat.com>
 LABEL Description="ssh-cert-authority"
+RUN apt-get update && apt-get install -y openssh-client && apt-get clean && rm -rf /var/lib/apt
 COPY ssh-cert-authority-linux-amd64.gz /usr/local/bin/ssh-cert-authority.gz
 RUN gunzip /usr/local/bin/ssh-cert-authority.gz
 RUN chmod +x /usr/local/bin/ssh-cert-authority
-RUN apt-get update
-RUN apt-get install -y openssh-client
 ENTRYPOINT ["ssh-agent", "/usr/local/bin/ssh-cert-authority", "runserver"]

Dockerfile-buildenv

@@ -1,12 +1,15 @@
-FROM ubuntu:14.04
+FROM ubuntu:15.10
 MAINTAINER Bob Van Zant <bob@veznat.com>
 LABEL Description="up-to-date ubuntu environment" Vendor="Cloudtools"
 
-RUN apt-get update && apt-get install -y \
-    build-essential \
-    curl \
-    git-core \
-    golang
+RUN apt-get update && \
+    apt-get install -y \
+        build-essential \
+        curl \
+        git-core \
+        golang && \
+    apt-get clean && \
+    rm -rf /var/lib/apt
 
 LABEL Description="up-to-date golang environment"