Fix update_application method

Returning 400 Bad Request errors.

Request body should be JSON encoded instead of application/x-www-form-urlencoded.

Author: timcraft

nexmo/__init__.py

@@ -235,7 +235,7 @@ def put(self, host, request_uri, params):
 
     params = dict(params, api_key=self.api_key, api_secret=self.api_secret)
 
-    return self.parse(host, requests.put(uri, data=params, headers=self.headers))
+    return self.parse(host, requests.put(uri, json=params, headers=self.headers))
 
   def delete(self, host, request_uri):
     uri = 'https://' + host + request_uri

test_nexmo.py

@@ -463,7 +463,8 @@ def test_update_application(self):
 
     self.assertIsInstance(self.client.update_application('xx-xx-xx-xx', params), dict)
     self.assertEqual(request_user_agent(), self.user_agent)
-    self.assertIn('answer_url=https%3A%2F%2Fexample.com%2Fncco', request_body())
+    self.assertEqual(request_content_type(), 'application/json')
+    self.assertIn(b'"answer_url": "https://example.com/ncco"', request_body())
 
   @responses.activate
   def test_delete_application(self):