Add test for nginx reverse proxy rule

Dockerfile

@@ -11,8 +11,13 @@ RUN apt-get update && apt-get install -y \
         wget -q -O $pkgname $pkgurl && dpkg -i $pkgname && rm $pkgname
 
 RUN luarocks install sitegen
-RUN luarocks install busted
-RUN luarocks install luajit-curl
+
+# needed for sitegen watcher
 RUN luarocks install inotify INOTIFY_INCDIR=/usr/include/x86_64-linux-gnu/
 
+# needed for testing
+RUN luarocks install busted
+RUN luarocks install luajit-curl
+RUN luarocks install luasocket # needed for testing nginx reverse proxy
+
 CMD ["sh", "-c", "openresty -p `pwd` -g 'daemon off;'"]