Added a note early on in the docuementation about memmap=True, and why you might want to use it.  This fixes #58.
Added a note early on in the docuementation about memmap=True, and why you might want to use it.  This fixes #58.

git-svn-id: 5305e2c1a78737cf7dd5f8f44e9bbbd00348fde7@1142 ed100bfc-0583-0410-97f2-c26b58777a21

spacetelescope/PyFITS,embray/PyFITS,embray/PyFITS,embray/PyFITS,embray/PyFITS,spacetelescope/PyFITS