Reduce add-on image size (#191)

Author: frenck

bookstack/Dockerfile

@@ -43,9 +43,10 @@ RUN \
     \
     && find /var/www/bookstack -type f -name "*.md" -depth -exec rm -f {} \; \
     && rm -f -r \
+         /root/.composer \
          /tmp/* \
-         /var/www/bookstack/tests \
-         /var/www/bookstack/dev
+         /var/www/bookstack/dev \
+         /var/www/bookstack/tests
 
 # Copy root filesystem
 COPY rootfs /