Streamline installation of packages

Dockerfile

@@ -8,22 +8,24 @@ ENV LANG en_US.UTF-8
 ENV LANGUAGE en_US:en
 ENV LC_ALL en_US.UTF-8
 
-# update and install some software requirements
-RUN apt-get update && apt-get upgrade -y && apt-get install -y curl wget git make sudo
-
-# For some reason, installing Elixir tries to remove this file
-# and if it doesn't exist, Elixir won't install. So, we create it.
-# Thanks Daniel Berkompas for this tip.
-# http://blog.danielberkompas.com
-RUN touch /etc/init.d/couchdb
-
-# download and install Erlang package
-RUN wget http://packages.erlang-solutions.com/erlang-solutions_1.0_all.deb \
- && dpkg -i erlang-solutions_1.0_all.deb \
- && apt-get update
-
-# install latest elixir package
-RUN apt-get install -y elixir erlang-dev erlang-parsetools && rm erlang-solutions_1.0_all.deb
+# update and install software
+RUN apt-get update && apt-get upgrade -y \
+    # install system depedencies
+    && apt-get install -y curl wget git make sudo \
+    # download and install Erlang apt repo package
+    && wget http://packages.erlang-solutions.com/erlang-solutions_1.0_all.deb \
+    && dpkg -i erlang-solutions_1.0_all.deb \
+    && apt-get update \
+    && rm erlang-solutions_1.0_all.deb \
+    # For some reason, installing Elixir tries to remove this file
+    # and if it doesn't exist, Elixir won't install. So, we create it.
+    # Thanks Daniel Berkompas for this tip.
+    # http://blog.danielberkompas.com
+    && touch /etc/init.d/couchdb \
+    # install latest elixir package
+    && apt-get install -y elixir erlang-dev erlang-parsetools \
+    # clean up after ourselves
+    && apt-get clean
 
 ENV PHOENIX_VERSION 1.2.0