Update natural_language_understanding_v1.py

I was getting this error:

NameError: name 'features' is not defined

found out that line no. 15:
features=[features.Entities(), features.Keywords()])
should be:
features=[Features.Entities(), Features.Keywords()])

Notice the uppercase 'F'.

Author: manishth

examples/natural_language_understanding_v1.py

@@ -12,6 +12,6 @@
 response = natural_language_understanding.analyze(
     text='Bruce Banner is the Hulk and Bruce Wayne is BATMAN! '
          'Superman fears not Banner, but Wayne.',
-    features=[features.Entities(), features.Keywords()])
+    features=[Features.Entities(), Features.Keywords()])
 
 print(json.dumps(response, indent=2))