title: what do these error messages mean?
body: <p>i'm in section 9 of the hartl rails tutorial, this def isn't making sense.  thoughts?  </p>
  
  <pre><code>1) User pages index 
   Failure/Error: visit users_path
   ActionView::Template::Error:
     wrong number of arguments (2 for 1)
   # ./app/helpers/users_helper.rb:3:in `gravatar_for'
   # ./app/views/users/index.html.erb:7:in `block in _app_views_users_index_html_erb__3004047397113020476_70255017945740'
   # ./app/views/users/index.html.erb:5:in `each'
   # ./app/views/users/index.html.erb:5:in `_app_views_users_index_html_erb__3004047397113020476_70255017945740'
   # ./spec/requests/user_pages_spec.rb:12:in `block (3 levels) in &lt;top (required)&gt;'
  
  
  
  2) User pages index should list each user
   Failure/Error: visit users_path
   ActionView::Template::Error:
     wrong number of arguments (2 for 1)
   # ./app/helpers/users_helper.rb:3:in `gravatar_for'
   # ./app/views/users/index.html.erb:7:in `block in _app_views_users_index_html_erb__3004047397113020476_70255017945740'
   # ./app/views/users/index.html.erb:5:in `each'
   # ./app/views/users/index.html.erb:5:in `_app_views_users_index_html_erb__3004047397113020476_70255017945740'
   # ./spec/requests/user_pages_spec.rb:12:in `block (3 levels) in &lt;top (required)&gt;'
  </code></pre>