DOC: Describe matlib.py funky namespace

Author: sethtroisi

numpy/matlib.py

@@ -1,6 +1,8 @@
 import numpy as np
 from numpy.matrixlib.defmatrix import matrix, asmatrix
-# need * as we're copying the numpy namespace (FIXME: this makes little sense)
+# Matlib.py contains all functions in the numpy namespace with a few
+# replacements. See doc/source/reference/routines.matlib.rst for details.
+# Need * as we're copying the numpy namespace.
 from numpy import *  # noqa: F403
 
 __version__ = np.__version__