Dockerfile.main.erb in iruby-0.5.0

- old
+ new

@@ -1,9 +1,7 @@
 FROM iruby-test-base:ruby-<%= ruby_version %>
 
-RUN gem install cztop \
-    && gem install rbczmq -- --with-system-libs
-
+RUN gem install cztop
 RUN mkdir -p /iruby
 ADD . /iruby
 WORKDIR /iruby
 RUN bundle install