leverage docker caching mechanism and improve readability

Dockerfile

@@ -4,34 +4,25 @@ FROM debian:wheezy-backports
 ENV restyaboard_version=v0.2
 
 # update & install package
-RUN \
- apt-get update -y &&\
- apt-get install -y zip curl cron postgresql nginx &&\
- apt-get install -y php5 php5-fpm php5-curl php5-pgsql php5-imagick libapache2-mod-php5 &&\
- echo "postfix postfix/mailname string example.com"\
- | debconf-set-selections &&\
- echo "postfix postfix/main_mailer_type string 'Internet Site'"\
- | debconf-set-selections &&\
- apt-get install -y postfix
+RUN apt-get update --yes
+RUN apt-get install --yes zip curl cron postgresql nginx
+RUN apt-get install --yes php5 php5-fpm php5-curl php5-pgsql php5-imagick libapache2-mod-php5
+RUN echo "postfix postfix/mailname string example.com" | debconf-set-selections \
+        && echo "postfix postfix/main_mailer_type string 'Internet Site'" | debconf-set-selections \
+        && apt-get install -y postfix
 
 # deploy app
-RUN \
- curl -L -o /tmp/restyaboard.zip \
-  https://github.com/RestyaPlatform/board/releases/download/${restyaboard_version}/board-${restyaboard_version}.zip &&\
- unzip /tmp/restyaboard.zip -d /usr/share/nginx/html &&\
- rm /tmp/restyaboard.zip
+RUN curl -L -o /tmp/restyaboard.zip https://github.com/RestyaPlatform/board/releases/download/${restyaboard_version}/board-${restyaboard_version}.zip \
+        && unzip /tmp/restyaboard.zip -d /usr/share/nginx/html \
+        && rm /tmp/restyaboard.zip
 
 # setting app
 WORKDIR /usr/share/nginx/html
-RUN \
- cp -R media /tmp/ &&\
- cp restyaboard.conf /etc/nginx/conf.d &&\
- sed -i 's/^.*listen.mode = 0660$/listen.mode = 0660/'\
-  /etc/php5/fpm/pool.d/www.conf &&\
- sed -i 's|^.*fastcgi_pass.*$|fastcgi_pass unix:/var/run/php5-fpm.sock;|'\
-  /etc/nginx/conf.d/restyaboard.conf &&\
- sed -i -e "/fastcgi_pass/a fastcgi_param HTTPS 'off';"\
-  /etc/nginx/conf.d/restyaboard.conf
+RUN cp -R media /tmp/ \
+        && cp restyaboard.conf /etc/nginx/conf.d \
+        && sed -i 's/^.*listen.mode = 0660$/listen.mode = 0660/' /etc/php5/fpm/pool.d/www.conf \
+        && sed -i 's|^.*fastcgi_pass.*$|fastcgi_pass unix:/var/run/php5-fpm.sock;|' /etc/nginx/conf.d/restyaboard.conf \
+        && sed -i -e "/fastcgi_pass/a fastcgi_param HTTPS 'off';" /etc/nginx/conf.d/restyaboard.conf
 
 # volume
 VOLUME /usr/share/nginx/html/media