Specify bundler version compatible with ruby 1.9.3

Dockerfile

@@ -7,7 +7,7 @@ FROM bikebike/bikebike
 MAINTAINER Jonathan Rosenbaum <gnuser@gmail.com>
 
 RUN git clone git://github.com/asalant/freehub.git
-RUN gem install bundler
+RUN gem install bundler -v 1.15.4
 #RUN apt-get -y install ruby-dev
 RUN bundle install --gemfile=/freehub/Gemfile
 RUN service mysql start; cd /freehub; rake db:create:all; rake db:migrate; rake db:fixtures:load
@@ -17,4 +17,4 @@ COPY  freehub.conf /etc/supervisor/conf.d/
 
 CMD ["supervisord", "-c", "/etc/supervisor/supervisord.conf"]
 
-# docker run -d -p 3000:3000 --name="freehub" bikebike/freehub 
+# docker run -d -p 3000:3000 --name="freehub" bikebike/freehub