WARC: from_response incompatible with Requests>=1.0.0

## Description/Summary

Seems like warc-0.2.1 is incompatible with requests>=1.0.0. All that needs to be changed is to strip 'full' from 'full_url' and everything will work just fine again.
## Environment details:

Python 2.7
warc 0.2.1
Requests 1.0.4
## Example code

``` python
#!/usr/bin/python
import warc, requests

print warc.WARCRecord.from_response(requests.get("http://archive.org"))
```
## Traceback

``` python
>>> warc.WARCRecord.from_response(requests.get("http://archive.org"))
Traceback (most recent call last):
File "", line 1, in
File "/home/ersi/venv/lib/python2.7/site-packages/warc/warc.py", line 240, in from_response
"WARC-Target-URI": response.request.full_url.encode('utf-8')
AttributeError: 'PreparedRequest' object has no attribute 'full_url'
```