Pass a parameter called 'json' instead of 'format'.

This follows @codingjoe's suggested approach, which I diverged from earlier.

README.rst

@@ -145,7 +145,7 @@ Getting machine readable JSON reports
 
 If you want machine readable status reports you can request the ``/ht/``
 endpoint with the ``Accept`` HTTP header set to ``application/json``
-or pass ``format=json`` as a query parameter.
+or pass ``json=1`` as a query parameter.
 
 The backend will return a JSON response:
 
@@ -166,9 +166,9 @@ The backend will return a JSON response:
         "S3BotoStorageHealthCheck": "working"
     }
 
-    $ curl -v -X GET http://www.example.com/ht/?format=json
+    $ curl -v -X GET http://www.example.com/ht/?json=1
 
-    > GET /ht/?format=json HTTP/1.1
+    > GET /ht/?json=1 HTTP/1.1
     > Host: www.example.com
     >
     < HTTP/1.1 200 OK

health_check/views.py

@@ -46,7 +46,7 @@ def _run(plugin):
         accept_format = request.META.get('HTTP_ACCEPT', '')
         accepts_json = 'application/json' in accept_format
 
-        if accepts_json or request.GET.get('format') == 'json':
+        if accepts_json or request.GET.get('json', False):
             return self.render_to_response_json(plugins, status_code)
         else:
             context = {'plugins': plugins, 'status_code': status_code}

tests/test_views.py

@@ -95,7 +95,7 @@ def run_check(self):
 
         plugin_dir.reset()
         plugin_dir.register(JSONSuccessBackend)
-        response = client.get(self.url, {'format': 'json'})
+        response = client.get(self.url, {'json': 1})
         assert response.status_code == 200, response.content.decode('utf-8')
         assert response['content-type'] == 'application/json'
         assert json.loads(response.content.decode('utf-8')) == \
@@ -108,7 +108,7 @@ def run_check(self):
 
         plugin_dir.reset()
         plugin_dir.register(JSONErrorBackend)
-        response = client.get(self.url, {'format': 'json'})
+        response = client.get(self.url, {'json': 1})
         assert response.status_code == 500, response.content.decode('utf-8')
         assert response['content-type'] == 'application/json'
         assert 'JSON Error' in json.loads(response.content.decode('utf-8'))[JSONErrorBackend().identifier()]