allow admin to log in as other user

Gemfile
  gem 'pretender'                           #admin fakes being someone else
bundle install
app/controllers/application_controller.rb
  impersonates :user    #pretender gem
app/controllers/users_controller.rb
  skip_before_action :require_admin, only: :stop_impersonating
  set user before impersonate
  def impersonate
  def stop_impersonating
app/views/layouts/application.html.haml
  conditional link to stop impersonating, and notice if you are
app/views/users/index.html.haml
  %h1=t '.title', :default => 'User Administration Page'
  change btn-mini to btn-default
  change email to link to email
app/views/users/show.html.haml
    add block / unblock
    add impersonate
config/routes.rb
      get 'impersonate'
      get 'stop_impersonating'
spec/features/useradmins_spec.rb
+  describe 'Show' do
+    it 'lets the admin sign in as another user' do
+    it 'and we can sign back out' do
.rspec
    stop warnings for rspec