Add a Dockerfile for Unison 2.48.4 and Ocaml 4.03

What
===
Add a Dockerfile for Unison 2.48.4 and Ocaml 4.03.

Why
===
On macOS Sierra these are now the versions installed when using brew,
addressing issue #18.

Dockerfile-unison2.48.4-ocaml4.03

@@ -0,0 +1,31 @@
+FROM phusion/baseimage:0.9.16
+CMD ["/sbin/my_init"]
+
+MAINTAINER Leigh McCulloch
+
+# Upload Unison for building
+COPY container /
+
+# Allow setting these on build
+ARG UNISON_VERSION=2.48.4
+ARG OCAML_VERSION=4.03
+
+# Build and install Unison versions then cleanup
+RUN apt-get update -y \
+ && curl -LO http://download.opensuse.org/repositories/home:ocaml/xUbuntu_14.04/Release.key \
+ && apt-key add - < Release.key \
+ && apt-get update -y \
+ && dependencies-install.sh \
+ && unison-install.sh \
+ && dependencies-purge.sh \
+ && rm -rf /var/lib/{apt,dpkg,cache,log}/ /tmp/* /var/tmp/*
+
+# Set default Unison configuration
+ENV UNISON_WORKING_DIR=/unison
+
+# Set working directory to be the home directory
+WORKDIR /root
+
+# Setup unison to run as a service
+VOLUME $UNISON_WORKING_DIR
+EXPOSE 5000

Makefile

@@ -1,4 +1,5 @@
 build:
+	sed -e "s/\$${UNISON_VERSION}/2.48.4/"   -e "s/\$${OCAML_VERSION}/4.03/" Dockerfile > Dockerfile-unison2.48.4-ocaml4.03
 	sed -e "s/\$${UNISON_VERSION}/2.48.3/"   -e "s/\$${OCAML_VERSION}/4.02/" Dockerfile > Dockerfile-unison2.48.3-ocaml4.02
 	sed -e "s/\$${UNISON_VERSION}/2.48.3/"   -e "s/\$${OCAML_VERSION}/4.01/" Dockerfile > Dockerfile-unison2.48.3-ocaml4.01
 	sed -e "s/\$${UNISON_VERSION}/2.40.102/" -e "s/\$${OCAML_VERSION}/4.02/" Dockerfile > Dockerfile-unison2.40.102-ocaml4.02