I am getting
IOError: [Errno 13] Permission denied: \'/usr/local/lib/python2.7/dist-packages/python_dateutil-2.2-py2.7.egg/EGG-INFO/top_level.txt\'
I was just having similar issues on my machine. Pip wasn't letting my install anything because nothing could be written to my site-packages directory. Not in love with this but I ran sudo chown -R $USER /Library/Python/2.7/site-packages/
and now Pip has no problem writing to my site-packages directory.