Addressing review comments

Author: Kavya Srinet

doc/api/v2/fluid/io.rst

@@ -4,7 +4,7 @@ IO
 
 
 
-isParameter
+is_parameter
 -----------
 ..  autofunction:: paddle.v2.fluid.io.is_parameter
     :noindex:

python/paddle/v2/fluid/io.py

@@ -11,15 +11,15 @@
 
 
 def is_parameter(var):
-    """Check whether the variable is a Parameter
+    """Check whether the variable is a Parameter.
 
     This function checks whether the input variable is a Parameter.
 
     Args:
         var : The input variable.
 
     Returns:
-        boolean result whether the variable is a Parameter
+        boolean result whether the variable is a Parameter.
     """
     return isinstance(var, Parameter)