Update Dockerfile to use alpine linux image

.dockerignore

@@ -1,3 +1,3 @@
 node_modules
 .git
-.env
+.env

Dockerfile

@@ -1,11 +1,21 @@
-FROM iojs:slim
+FROM mhart/alpine-node
 MAINTAINER Jonathan Cremin <jonathan@crem.in>
 
-ADD   package.json package.json
-RUN   npm install
-COPY  . .
+WORKDIR /app
+
+RUN apk add --update make gcc g++ python git
+
+COPY package.json package.json
+
+RUN npm install
+
+RUN apk del make gcc g++ python git && \
+  rm -rf /tmp/* /var/cache/apk/* /root/.npm /root/.node-gyp
+
+COPY . .
+
+RUN npm run build
 
-RUN   npm run build
 EXPOSE 3000
 
-CMD   npm start
+CMD ["npm", "start"]