l3d#78 Make composer executable writable to allow selfupdate for regular users

Dockerfile

@@ -82,6 +82,7 @@ RUN echo 'hosts: files dns' > /etc/nsswitch.conf && \
     \
     wget -q https://github.com/docker/compose/releases/download/${compose_version}/docker-compose-`uname -s`-`uname -m` -O /usr/local/bin/docker-compose && \
     chmod +x /usr/local/bin/docker-compose && \
+    chmod ugo+w /usr/local/bin/composer && \
     \
     wget -q https://getcomposer.org/composer.phar -O /usr/local/bin/composer && \
     chmod +x /usr/local/bin/composer && \