Feature/python requests

Trying to replace pycurl with python-requests.

I haven't had a chance to test this too much.. only with with the following script.

```python
#!/usr/bin/env python

import fedora.client
c = fedora.client.ProxyClient("https://admin.fedoraproject.org/pkgdb")
print c.send_request("/collections/")
```

We need to test some of the other web services and especially the file uploading stuff -- I am most uncertain about that.  I've got to go for the night but am posting this here for meanwhile discussion.