Streaming-httplib2

Changed behaviour to return file like object instead of strings for content.
Changed cache to handle streaming too.

Fix failure to install cacerts.txt for 2.x installs.

The two major changes in this release are SSL Certificate
checking and App Engine support. By default the certificates
of an HTTPS connection are checked, but that can be disabled
via disable_ssl_certificate_validation. The second change
is that on App Engine there is a new connection object
that utilizes the urlfetch capabilities on App Engine, including
setting timeouts and validating certificates.

The following issues have been addressed:

Fixes issue 72. Always lowercase authorization header.
Fix issue 47. Redirects that become a GET should not have a body.
Fixes issue 19. Set Content-location on redirected HEAD requests
Fixes issue 139. Redirect with a GET on 302 regardless of the originating method.
Fixes issue 138. Handle unicode in headers when writing and retrieving cache entries. Who says headers have to be ASCII!
Add certificate validation. Work initially started by Christoph Kern.
Set a version number. Fixes issue 135.
Sync to latest version of socks.py
Add gzip to the user-agent, in case we are making a request to an app engine project: http://code.google.com/appengine/kb/general.htmlcompression
Uses a custom httplib shim on App Engine to wrap urlfetch, as opposed
Add default support for optimistic concurrency on PATCH requests
Fixes issue 126. IPv6 under various conditions would fail.
Fixes issue 131. Handle socket.timeout's that occur during send.
proxy support: degrade gracefully when socket.socket is unavailable

The following issues have been addressed:

51 - Failure to handle server legitimately closing connection before request body is fully sent
77 - Duplicated caching test
65 - Transform _normalize_headers into a method of Http class
45 - Vary header
73 - All files in Mercurial are executable
81 - Have a useful .hgignore
78 - Add release tags to the Mercurial repository
67 - HEAD requests cause next request to be retried

Mostly bug fixes, the big enhancement is the addition of proper Vary: header
handling. Thanks to Chris Dent for that change.

The other big change is the build process for distributions so that both python2 and python3
are included in the same .tar.gz/.zip file.

Added Python 3 support

Fixed the following bugs:

12 - Cache-Control: only-if-cached incorrectly does request if item not in cache
39 - Deprecation warnings in Python 2.6
54 - Http.request fails accesing Google account via http proxy
56 - Block on response.read() for HEAD requests.
57 - Timeout ignore for Python 2.6
58 - Fixed parsing of Cache-Control: header to make it more robust

Also fixed a deprecation warning that appeared between Python 3.0 and 3.1.

Added support for proxies if the Socksipy module is installed.

Fixed bug with some HEAD responses having content-length set to
zero incorrectly.

Fixed most except's to catch a specific exception.

Added 'connection_type' parameter to Http.request().

The default for 'force_exception_to_status_code' was changed to False. Defaulting
to True was causing quite a bit of confusion.