added tests for batch API endpoint

test/batch.test.js

+describe('FullContact.Batch', function () {
+  'use strict';
+
+  var FullContact = require('../');
+  var chai = require('chai');
+
+  chai.config.includeStack = true;
+
+  //
+  // The API key we use for testing.
+  //
+  var key = process.env.API_KEY;
+  if (!key) {
+    throw new Error('Please provide your API using the API_KEY env variable.');
+  }
+
+  //
+  // Some of the requests take a really long time, so set a really long timeout
+  //
+  this.timeout(20000);
+
+  //
+  // Create a multi API instance
+  //
+  var multi = new FullContact(key).multi();
+
+  describe('#multi', function () {
+    it('batches two requests', function (done) {
+      multi.person.twitter('observe_it');
+      multi.person.twitter('jack');
+      
+      multi.exec(done);
+    });
+
+    it('provides the proper casing');
+  });
+});