add checkout subbmission directive

app/assets/javascripts/darkswarm/directives/submit_checkout.js.coffee

@@ -0,0 +1,13 @@
+Darkswarm.directive "submitCheckout", () ->
+  restrict: "A"
+  link: (scope, elm, attr)->
+    elm.bind 'click', (ev)->
+      ev.preventDefault()
+
+      names = ["details", "billing", "shipping", "payment"]
+      for name of names
+        if not scope[name].$valid
+          $scope.show name
+      # else
+      #   scope.purchase(ev)
+