Add CONTRIBUTING.rst file with instructions to contribute

Also link to the file from the README.txt file.

Change-Id: I7dd74ce2a6d575a5503755d1aba2983907ccb7c9

.gitattributes

@@ -3,6 +3,8 @@
 /GitSetup        export-ignore
 /SetupForDevelopment.sh  export-ignore  eol=lf
 
+/CONTRIBUTING.rst conflict-marker-size=78
+
 *.c              whitespace=tab-in-indent,no-lf-at-eof
 *.h              whitespace=tab-in-indent,no-lf-at-eof
 *.h.in           whitespace=tab-in-indent,no-lf-at-eof

CONTRIBUTING.rst

+Contributing to KWSys
+*********************
+
+Overview
+========
+
+KWSys is kept in its own Git repository and shared by several projects
+via copies in their source trees.  Changes to KWSys should not be made
+directly in a host project, except perhaps in maintenance branches.
+
+Please visit
+
+  http://public.kitware.com/Wiki/KWSys/Git
+
+to contribute changes directly to KWSys upstream.  Once changes are
+reviewed, tested, and integrated there then the copies of KWSys within
+dependent projects can be updated to get the changes.
+
+Issues
+======
+
+KWSys has no independent issue tracker.  After encountering an issue
+(bug) please try to submit a patch using the above instructions.
+Otherwise please report the issue to the tracker for the project that
+hosts the copy of KWSys in which the problem was found.
+
+License
+=======
+
+We do not require any formal copyright assignment or contributor license
+agreement.  Any contributions intentionally sent upstream are presumed
+to be offerred under terms of the OSI-approved BSD 3-clause License.
+See `Copyright.txt`_ for details.
+
+.. _`Copyright.txt`: Copyright.txt

README.txt

@@ -8,3 +8,5 @@ details.
 You are probably reading this file in the source tree of a surrounding
 project.  In that case, see "../README.kwsys" for details of using
 KWSys in your project.
+
+See CONTRIBUTING.rst for instructions to contribute KWSys changes.