title: "No explicit conversion of Symbol into String" for new records in rails 4.0.1 (only)
body: <p>After my rails 4 upgrade, trying to create a new record for any of my ActiveRecord classes gives</p>
  
  <pre><code>No explicit conversion of Symbol into String
  </code></pre>
  
  <p>For example, here is my links links_params method</p>
  
  <pre><code>def link_params
    params.require(:link)
    .permit(:url_address, :group_id, :alt_text, :version_number, 
    :position, :content_date, :verified_date) # This is line 157
  end
  
  # line 118 is: @link = Link.new(link_params)
  </code></pre>
  
  <p>but I get</p>
  
  <pre><code>TypeError (no implicit conversion of Symbol into String):
    app/controllers/links_controller.rb:157:in `link_params'
    app/controllers/links_controller.rb:118:in `create'
  
  This error occurred while loading the following files:
  link
  
  Parameters:
  
  {"utf8"=&gt;"✓",
   "authenticity_token"=&gt;"0FqFTx2EjCIO+R+rm97lF15+id4b452n+dBuUNxAL9U=",
   "link"=&gt;{"url_address"=&gt;"http://www.google.com",
   "alt_text"=&gt;"",
   "version_number"=&gt;"",
   "group_id"=&gt;"49",
   "content_date"=&gt;"08/18/2014"},
   "commit"=&gt;"Save"}
  </code></pre>