updating NLU version date to be consistent with the version date we're using in the docs, the other SDKs, and in the NLU code

Author: kcheat

examples/natural_language_understanding_v1.py

@@ -14,7 +14,7 @@
 # In[3]:
 
 nlu = watson_developer_cloud.NaturalLanguageUnderstandingV1(
-    version='2016-01-23',
+    version='2017-02-27',
     username='USERNAME',
     password='PASSWORD')
 

watson_developer_cloud/natural_language_understanding_v1.py

@@ -22,9 +22,9 @@ class NaturalLanguageUnderstandingV1(WatsonDeveloperCloudService):
     from watson_developer_cloud/natural_language_understanding/features/v1
 
     """
-    base_url = 'https://gateway.watsonplatform.net'
+    base_url = 'https://gateway-s.watsonplatform.net'
     default_url = '{0}/natural-language-understanding/api'.format(base_url)
-    latest_version = '2017-01-23'
+    latest_version = '2017-02-27'
 
     def __init__(self,
                  version,