- Fairly significant changes to include Vivian's patches for improved pdb

support.  Her original idea was kept in full, code reworked for compactness
and better integration with the rest of ipython.

- Added download_url arg to setup.py to support setuptools.

setup.py

@@ -133,6 +133,7 @@ setup(name             = name,
       author           = authors['Fernando'][0],
       author_email     = authors['Fernando'][1],
       url              = url,
+      download_url     = download_url,
       license          = license,
       platforms        = platforms,
       keywords         = keywords,