update Integer field docs

Author: Kevin Burke

docs/fields.rst

@@ -54,7 +54,7 @@ Renaming Attributes
 -------------------
 
 Often times your public facing field name is different from your internal
-attribute naming.  To configure this mapping, use the ``attribute`` kwarg. ::
+attribute naming. To configure this mapping, use the ``attribute`` kwarg. ::
 
     fields = {
         'name': fields.String(attribute='private_name'),

flask_restful/fields.py

@@ -176,6 +176,15 @@ def format(self, value):
 
 
 class Integer(Raw):
+    """ Field for outputting an integer value.
+
+    :param int default: The default value for the field, if no value is
+        specified.
+
+    :param attribute: If the public facing value differs from the internal
+        value, use this to retrieve a different attribute from the response
+        than the publicly named value.
+    """
     def __init__(self, default=0, attribute=None):
         super(Integer, self).__init__(default, attribute)