Added better clarification about PyFITS' behavior w.r.t. checksums, per #148.
Added better clarification about PyFITS' behavior w.r.t. checksums, per #148.

git-svn-id: 5305e2c1a78737cf7dd5f8f44e9bbbd00348fde7@1504 ed100bfc-0583-0410-97f2-c26b58777a21

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