Add gem install bundler to installation guide

Created by: pschultz

bundler was missing when I followed this guide. Ubuntu points you to the ruby-bundler, which is based on ruby 1.8 and doesn't work. Installing bundler with gem works.

This PR adds the command to do that to the installation guide.

app/views/teams/show.js.haml

+:plain 
+  Pager.append(#{@events.count}, "#{escape_javascript(render(@events))}");