Integrate pre-fetching plan and phase from 25e2669

after_save callback for answer model with tests. #154

rake task to update completed plans. #154

statistics#completed_plans action done. #154

HTML view for completed plans and tweaks to JS file associated. #154

completed_plans action started. DMPRoadmap/roadmap#154

usage#index action and server view completed. Started dynamic UI through JS.

added moment js library and ajaxified joined_users stats.

charts.js integration for users joined. DMPRoadmap/roadmap#154