install from tar; reduce image size

Integrating changes from @DexterTheDragon on latest version. Fixes #11 and #17

Dockerfile

@@ -2,8 +2,8 @@ FROM ubuntu
 MAINTAINER Christian Lück <christian@lueck.tv>
 
 RUN DEBIAN_FRONTEND=noninteractive apt-get update && apt-get install -y \
-  nginx git supervisor php5-fpm php5-cli php5-curl php5-gd php5-json \
+  nginx supervisor php5-fpm php5-cli php5-curl php5-gd php5-json \
-  php5-pgsql php5-mysql php5-mcrypt && apt-get clean
+  php5-pgsql php5-mysql php5-mcrypt && apt-get clean && rm -rf /var/lib/apt/lists/*
 
 # enable the mcrypt module
 RUN php5enmod mcrypt
@@ -14,10 +14,12 @@ RUN ln -s /etc/nginx/sites-available/ttrss /etc/nginx/sites-enabled/ttrss
 RUN rm /etc/nginx/sites-enabled/default
 
 # install ttrss and patch configuration
-RUN git clone https://github.com/gothfox/Tiny-Tiny-RSS.git /var/www
 WORKDIR /var/www
+RUN apt-get update && DEBIAN_FRONTEND=noninteractive apt-get install -y curl --no-install-recommends && rm -rf /var/lib/apt/lists/* \
+    && curl -SL https://tt-rss.org/gitlab/fox/tt-rss/repository/archive.tar.gz?ref=master | tar xzC /var/www --strip-components 1 \
+    && apt-get purge -y --auto-remove curl \
+    && chown www-data:www-data -R /var/www
 RUN cp config.php-dist config.php
-RUN chown www-data:www-data -R /var/www
 
 # expose only nginx HTTP port
 EXPOSE 80
@@ -34,4 +36,3 @@ ENV DB_PASS ttrss
 ADD configure-db.php /configure-db.php
 ADD supervisord.conf /etc/supervisor/conf.d/supervisord.conf
 CMD php /configure-db.php && supervisord -c /etc/supervisor/conf.d/supervisord.conf
-