title: Import CSV Data in a Rails App with ActiveAdmin
body: <p>i want to upload CSV files through the activeadmin panel.</p>
  
  <p>on the index page from the resource "product" i want a button next to the "new product" button with "import csv file".</p>
  
  <p>i dont know where to start.
  in the documentation is something about collection_action, but with the code below i have no link at the top. </p>
  
  <pre><code>ActiveAdmin.register Post do
      collection_action :import_csv, :method =&gt; :post do
        # Do some CSV importing work here...
        redirect_to :action =&gt; :index, :notice =&gt; "CSV imported successfully!"
      end
    end
  </code></pre>
  
  <p>anyone here who use activeadmin and can import csv data?</p>