Allow optionally disabling ssl compression

By default SSL layer compression is enabled when connecting to a https server.

Disabling compression can provide a performance increase, particularly when transferring
objects over a fast network.

Here's an example of download performance with and without SSL compression (actually this was done
for Glance, but the principle is the same):

http://15.185.160.228/ssl_comp.pdf

The ability to disable ssl compression would require using the python-openssl library, eg (a working
prototype):

http://15.185.160.228/ssl-comp-diff.txt

Note that much of the functionality in python-openssl maps to Python 3.3 so if/when we move to a newer version of Python replacing the python-openssl code with Python 3.3 code should be simple.