Fix pip to work with the --extra-index-url option.
Fix pip to work with the --extra-index-url option.

For example, easy_installing TurboGears2 entails:

	easy_install -i http://www.turbogears.org/2.0/downloads/current/index tg.devtools

yet, adding the extra index url in pip doesn't seem to work:

	./pip.py bundle Moksha.pybundle -r stable-reqs.txt --extra-index-url=http://www.turbogears.org/2.0/downloads/current/index

This change seems to fix this issue, allowing us to create Moksha bundles
containing TurboGears2.

pombredanne/moksha,mokshaproject/moksha,mokshaproject/moksha,ralphbean/moksha,lmacken/moksha,pombredanne/moksha,mokshaproject/moksha,ralphbean/moksha,pombredanne/moksha,ralphbean/moksha,lmacken/moksha,mokshaproject/moksha,lmacken/moksha,pombredanne/moksha