deprecate `pip bundle` and support for installing pybundle files
pip-1.4rc4
have pip release branch test using virtualenv release branch
pip.index: fix crash getting Content-Type header

Returned headers may not always have the "Content-Type"
field available.  Avoid KeyError exceptions by using
dict.get() instead of blindly grabbing the header value.

Closes #32
fix for http://bugs.python.org/issue17980 in code backported from the python3 stdlib

Signed-off-by: Marcus Smith <qwcode@gmail.com>
1.4rc5
merge from release-1.4 branch