add "submit" method to Node that allows to submit a form node without clicking a button

lib/capybara/driver/webkit/node.rb

@@ -77,6 +77,10 @@ class Capybara::Driver::Webkit
       invoke "path"
     end
 
+    def submit(opts)
+      invoke "submit"
+    end
+
     def trigger(event)
       invoke "trigger", event
     end

src/capybara.js

@@ -97,6 +97,10 @@ Capybara = {
     return this.nodes[index].tagName.toLowerCase();
   },
 
+  submit: function(index) {
+    return this.nodes[index].submit();
+  },
+
   click: function (index) {
     var clickEvent = document.createEvent('MouseEvents');
     clickEvent.initMouseEvent('click', true, true, window, 0, 0, 0, 0, 0, false, false, false, false, 0, null);