DOC: point to nipy organization's nibabel instead of the original Michael's for issues and changes

Author: yarikoptic

Changelog

@@ -11,11 +11,11 @@ releases for both packages.
 
 'Close gh-' statements refer to GitHub issues that are available at::
 
-  http://github.com/hanke/nibabel/issues
+  http://github.com/nipy/nibabel/issues
 
 The full VCS changelog is available here:
 
-  http://github.com/hanke/nibabel/commits/master
+  http://github.com/nipy/nibabel/commits/master
 
 Releases
 ~~~~~~~~