stringify non-string paths to avoid Rails' .to_json implementation on Pathname objects

lib/capybara/poltergeist/browser.rb

@@ -104,7 +104,7 @@ module Capybara::Poltergeist
     end
 
     def render(path, options = {})
-      command 'render', path, !!options[:full]
+      command 'render', path.to_s, !!options[:full]
     end
 
     def resize(width, height)

spec/integration/driver_spec.rb

@@ -95,6 +95,14 @@ module Capybara::Poltergeist
       end
     end
 
+    it 'supports rendering the page with a nonstring path' do
+      file = POLTERGEIST_ROOT + '/spec/tmp/screenshot.png'
+      FileUtils.rm_f file
+      @driver.visit('/')
+      @driver.render(Pathname(file))
+      File.exist?(file).should == true
+    end
+
     it 'supports executing multiple lines of javascript' do
       @driver.execute_script <<-JS
         var a = 1