Use stable branches instead of releases from tags

Part of #6 and #7

Dockerfile

@@ -13,11 +13,14 @@ RUN apt-get update && apt-get install -y \
     libxml2-dev libxslt-dev \
     && rm -rf /var/cache/apt /var/lib/apt/lists /etc/ssh_host_*
 
+# We don't use release tags but the stable branches from
+# https://github.com/taigaio/taiga-back/tree/stable
+
 ## backend
-RUN curl -L https://github.com/taigaio/taiga-back/archive/3.1.0.tar.gz | tar -xz -C /app/code/taiga-back --strip-components 1 -f -
+RUN curl -L https://github.com/taigaio/taiga-back/archive/e75510507c22d5938b6f9b19b554483e4390ccd8.tar.gz | tar -xz -C /app/code/taiga-back --strip-components 1 -f -
 
 ## frontend
-RUN curl -L https://github.com/taigaio/taiga-front-dist/archive/3.1.0-stable.tar.gz | tar -xz -C /app/code/taiga-front-dist --strip-components 1 -f -
+RUN curl -L https://github.com/taigaio/taiga-front-dist/archive/93bbd82a983d3f7f694bfe3d460221d6ae6701ba.tar.gz | tar -xz -C /app/code/taiga-front-dist --strip-components 1 -f -
 
 ADD build.sh nginx.conf conf.json conf_ldap.json local.py local_ldap.py start.sh /app/code/