Improve development workflow in Dockerfile

We should leverage docker caching so builds take less time.

Author: maxjacobson

Dockerfile

@@ -3,8 +3,6 @@ FROM alpine:edge
 MAINTAINER Code Climate <[email protected]>
 
 WORKDIR /usr/src/app
-COPY . /usr/src/app
-
 # Install PHP
 RUN apk --update add \
       php7 \
@@ -23,13 +21,18 @@ RUN apk --update add \
     rm /var/cache/apk/* && \
     ln -s /usr/bin/php7 /usr/bin/php
 
+COPY composer.json /usr/src/app/composer.json
+COPY composer.lock /usr/src/app/composer.lock
+
 RUN apk --update add curl && \
     curl -sS https://getcomposer.org/installer | php && \
     ./composer.phar install && \
     apk del curl && \
     rm /usr/src/app/composer.phar \
        /var/cache/apk/*
 
+COPY bin/build-content /usr/src/app/bin/build-content
+
 # Build Content
 RUN apk --update add build-base ca-certificates ruby ruby-dev && \
     gem install json httparty --no-rdoc --no-ri && \
@@ -38,6 +41,8 @@ RUN apk --update add build-base ca-certificates ruby ruby-dev && \
     apk del build-base ca-certificates ruby ruby-dev && \
     rm /var/cache/apk/*
 
+COPY . /usr/src/app
+
 RUN adduser -u 9000 -D app
 RUN chown -R app:app .