move require_data kwarg to end of parameter list

So that calls to validate() passing positional arguments
continue to work.

flasgger/utils.py

@@ -288,9 +288,9 @@ def __replace_ref(schema, relative_path):
 
 
 def validate(
-        data=None, require_data=True, schema_id=None, filepath=None,
-        root=None, definition=None, specs=None, validation_function=None,
-        validation_error_handler=None):
+        data=None, schema_id=None, filepath=None, root=None, definition=None,
+        specs=None, validation_function=None, validation_error_handler=None,
+        require_data=True):
     """
     This method is available to use YAML swagger definitions file
     or specs (dict or object) to validate data against its jsonschema.
@@ -300,7 +300,6 @@ def validate(
         validate(request.json, 'User', specs={'definitions': {'User': ...}})
 
     :param data: data to validate, by default is request.json
-    :param require_data: is the data param required?
     :param schema_id: The definition id to use to validate (from specs)
     :param filepath: definition filepath to load specs
     :param root: root folder (inferred if not provided), unused if path
@@ -316,6 +315,7 @@ def validate(
         exceptions thrown when validating which takes the exception
         thrown as the first, the data being validated as the second and
         the schema being used to validate as the third argument
+    :param require_data: is the data param required?
     """
     schema_id = schema_id or definition