added Docker file (fixes #1)

Dockerfile

@@ -0,0 +1,14 @@
+FROM    centos:centos6
+
+# Enable EPEL for Node.js
+RUN     rpm -Uvh http://download.fedoraproject.org/pub/epel/6/i386/epel-release-6-8.noarch.rpm
+# Install Node.js and npm
+RUN     yum install -y npm
+
+# Bundle app source
+COPY . /src
+# Install app dependencies
+RUN cd /src; npm install
+
+EXPOSE  3000
+CMD ["node", "/src/bin/www"]