title: wicked-pdf hangs server when generating file
body: <p>On a rails 3.2.18 application, with wicked_pdf (0.11.0) and wkhtmltopdf-binary (0.9.9.3) declared in the gem file, mime-types.rb was <strong>not</strong> amended to include<code>Mime::Type.register "application/pdf", :pdf</code> otherwise, on startup of Thin on osX development platform, the following warning is given:</p>
  
  <pre><code>/Users/it/.rvm/gems/ruby-1.9.3-p125@app/gems/actionpack-3.2.18/lib/action_dispatch/http/mime_type.rb:102: warning: already initialized constant PDF
  </code></pre>
  
  <p>An initializer states</p>
  
  <pre><code>WickedPdf.config = {
    :exe_path =&gt; '/usr/local/bin/wkhtmltopdf'
  }
  </code></pre>
  
  <p>The path <code>/usr/local/bin</code> does include an alias  to wkhtmltopdf.  In a show view:</p>
  
  <pre><code>  def show
      @transaction = Transaction.find(params[:id])
  
      respond_to do |format|
        format.html { render :layout =&gt; 'pdf' } # show.html.erb
        format.pdf do
          render :pdf =&gt; "invoice_name"
        end
        format.json { render json: @transaction }
      end
    end
  </code></pre>
  
  <p>The show view renders appropriately.  Append the path with <code>.pdf</code> and the console registers:</p>
  
  <pre><code>"***************[\"/usr/local/bin/wkhtmltopdf\", \"-q\", \"file:///var/folders/kV/kVDOSPkcEuqSVnTjenAVRE+++TI/-Tmp-/wicked_pdf20141018-1401-m614pd.html\", \"/var/folders/kV/kVDOSPkcEuqSVnTjenAVRE+++TI/-Tmp-/wicked_pdf_generated_file20141018-1401-1hor23g.pdf\"]***************"
  </code></pre>
  
  <p>And the server hangs.  It gets interrupted with <code>ctrl-c</code> and then the server console adds:</p>
  
  <pre><code>[...]
  Rendered transactions/show.pdf.erb (12.1ms)
  Rendered text template (0.0ms)
  Sent data invoice_name.pdf  (18.8ms)
  Completed 200 OK in 36322.7ms (Views: 15.2ms | ActiveRecord: 3.0ms)
  Exiting
  </code></pre>
  
  <p>which it did not do.  Other attempts to simply generate a file and save it have led to non-production of the PDF file, but without hanging the Thin server. So the engines are not all running properly...</p>
  
  <p>What is wrong with the set-up?</p>