Set the registry for node in prereqs

rakelib/prereqs.rake

 PREREQS_MD5_DIR = ENV["PREREQ_CACHE_DIR"] || File.join(REPO_ROOT, '.prereqs_cache')
+NPM_REGISTRY = "http://registry.npmjs.org/"
 
 CLOBBER.include(PREREQS_MD5_DIR)
 
@@ -11,6 +12,7 @@ desc "Install all node prerequisites for the lms and cms"
 task :install_node_prereqs => "ws:migrate" do
     unchanged = 'Node requirements unchanged, nothing to install'
     when_changed(unchanged, ['package.json']) do
+        sh("npm config set registry '#{NPM_REGISTRY}'")
         sh('npm install')
     end unless ENV['NO_PREREQ_INSTALL']
 end