Djproxy

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- Add a ``timeout`` configuration to HttpProxy views allowing
configuration of how quickly HttpProxy views give up on slow upstream
responses.
- Add a ``cert`` configuration option to HttpProxy views.
- Update ``generate_routes`` and ``generate_proxy`` to support new
configuration options.
- Documentation updates.
- Correct a development environment issue with six: a version that was
too low was specified in requirements.txt which caused test failures
in certain cases.

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- Adds python 3 support.

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- Adds a middleware that sends an X-Forwarded-Proto header to upstream
endpoints based on whether or not the incoming connection is https or
http.
- Adds the ``X-Forwarded-Proto`` middleware to HttpProxy views by
default.
- Resolves an issue that would cause djproxy to fail to install in
python 2.6 if django wasn't already installed.
- Adds a MANIFEST.in file so that relevant assets are bundled with
dists.

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- Renamed ``HttpProxy.igorned_downstream_headers`` to
``ignored_upstream_headers``
- Added middleware proxy functionality for modifying content, headers
before requests/responses are sent upstream or downstream.
- Moved XFF header functionality to a middleware
- Moved XFH header functionality to a middleware
- Moved reverse proxy functionality to a middleware
- Updated generate routes to support configuring middleware
- Reorganized the internal structure of the app for sanity's sake.

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- Disable CSRF checks by default for proxies created with
``generate_routes``

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- Makes HttpProxy SSL verification configurable via the ``verify_ssl``
class variable.