Added project menu, body_trackers#index and sidebar

app/controllers/body_trackers_controller.rb

@@ -1,5 +1,17 @@
 class BodyTrackersController < ApplicationController
+  before_action :find_project, only: [:index]
+  before_action :authorize
 
   def index
   end
+
+  private
+
+  # :find_* methods are called before :authorize,
+  # @project is required for :authorize to succeed
+  def find_project
+    @project = Project.find(params[:project_id])
+  rescue ActiveRecord::RecordNotFound
+    render_404
+  end
 end