add error if version_date isn't passed in on construction

Author: Joshua B. Smith

examples/natural_language_understanding.v1.js

@@ -1,7 +1,9 @@
 const fs = require('fs');
 const NaturalLanguageUnderstandingV1 = require('../natural-language-understanding/v1.js');
 
-const auth = {username: '<USERNAME>',password: '<PASSWORD>'};
+const auth = {username: '<USERNAME>',
+              password: '<PASSWORD>',
+              version_date= NaturalLanguageUnderstandingV1.VERSION_DATE};
 const nlu = new NaturalLanguageUnderstandingV1(auth);
 
 const query = new nlu.QueryBuilder();

natural-language-understanding/v1.js

@@ -28,6 +28,10 @@ var BaseService = require('../lib/base_service');
  */
 function NaturalLanguageUnderstandingV1(options) {
   BaseService.call(this, options);
+  if (typeof this._options.version_date === 'undefined') {
+    throw new Error('Argument error: version_date was not specified, use 2016-01-23');
+  }
+  this._options.qs.version = this._options.version_date;
 }
 util.inherits(NaturalLanguageUnderstandingV1, BaseService);
 NaturalLanguageUnderstandingV1.prototype.name = 'natural_language_understanding';
@@ -164,14 +168,12 @@ NaturalLanguageUnderstandingV1.prototype.analyze = function(query, params, callb
     params = params || {};
   }
 
-  params.version = params.version || NaturalLanguageUnderstandingV1.VERSION_DATE;
 
   var parameters = {
     options: {
       url: '/v1/analyze',
       method: 'POST',
       json: true,
-      qs: pick(params, ['version']),
       body: query.object()
     },
     defaultOptions: this._options

test/unit/test.natural_language_understanding.v1.js

@@ -16,14 +16,25 @@ describe('natural_language_understanding', function() {
   var nlu;
 
   before(function() {
-    nlu = new watson.NaturalLanguageUnderstandingV1({username: 'user', password: 'pass'});
+    nlu = new watson.NaturalLanguageUnderstandingV1({username: 'user',
+                                                     password: 'pass',
+                                                     version_date: watson.NaturalLanguageUnderstandingV1.VERSION_DATE});
     nock.disableNetConnect();
   });
 
   after(function() {
     nock.cleanAll();
   });
 
+  it('should throw if no version is present', function(done) {
+    assert.throws(function() {
+      const badnlu = new watson.NaturalLanguageUnderstandingV1({username: 'user',
+                                                                password: 'pass'});
+      assert(badnlu);
+    });
+    done();
+  });
+
   it('analyze()', function(done) {
     nock(watson.NaturalLanguageUnderstandingV1.URL)
       .persist()