[try] make schema and accept required in request schema

Fixes #602

Author: mohsen1

app/scripts/directives/tryoperation.js

@@ -116,6 +116,7 @@ SwaggerEditor.controller('TryOperation', function ($scope, formdataFilter,
     var schema = {
       type: 'object',
       title: 'Request',
+      required: ['scheme', 'accept'],
       properties: {
         scheme: {
           type: 'string',

test/e2e/specs/7_try_operation_test.js

@@ -40,7 +40,7 @@ describe('Try Operation', function () {
       .toContain('http://petstore-api.herokuapp.com/pet/?limit=11');
   });
 
-  xit('changing the scheme changes the request URL', function () {
+  it('changing the scheme changes the request URL', function () {
     $('.try-container select[name="root[scheme]"]').click();
     $('.try-container select[name="root[scheme]"] option:nth-child(2)').click();