Allow redirects through to user

For some reason flask.redirect returns a response that is derived from werkzeug.wrappers.Response, rather than flask.Response. Testing with some dummy code proves this problem to be a bit inconsistent:

```python
class X(object):
    def __init__(self):
        pass

class Y(X):
    def __init__(self):
        pass

z = Y()
isinstance(z, X)  #  -> True
```

This conflicts with what I see with Flask / Flask-Restful:

```python
from flask import Response

#...blahblahblah basic setup
x = redirect(url_for('render_root'))
isinstance(x, Response)  #  -> False
```

The code on this branch fixes this, but there may be a better way to fix this problem. I'd be open to hearing and possibly implementing any other ideas. Do you guys have any other thoughts?