[proxy] Stream data when forwarding, don't load into memory

[Allele Dev]

This is the problem line:

```python
    resp = requests.request(method, url, headers=request._headers,
                            data=request.stream.read()) # <---
```

python-requests accepts file-like objects. Unfortunately, a WSGI request is not enough of a file-like object to pass in naked. This will need to create some sort of wrapper to WSGI request objects to exposes the missing attributes to be able to pass in request.stream.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/49441

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/50328

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/50328
Committed: http://github.com/openstack/marconi/commit/66cd5af9b63bca49dee2e8206eece00c924a9cfe
Submitter: Jenkins
Branch: master

commit 66cd5af9b63bca49dee2e8206eece00c924a9cfe
Author: Alejandro Cabrera <email address hidden>
Date: Tue Oct 8 08:37:49 2013 -0400

    fix: stream request data rather than loading it into memory

    Change-Id: I47b1791de2a3d21b578604c1ea56f751cdb366ad
    Closes-Bug: 1230388