This patch adds a global timeout flag (viewable with `kubectl -h`) with
a default value of `0s` (meaning no timeout).

The timeout value is added to the default http client, so that zero
values and default behavior are enforced by the client.

**Example**
```
$ kubectl get pods # no timeout flag set - default to 0s (which means no
timeout)
NAME                      READY     STATUS    RESTARTS   AGE
docker-registry-1-h7etw   1/1       Running   1          2h
router-1-uv0f9            1/1       Running   1          2h

$ kubectl get pods --timeout=0 # zero means no timeout no timeout flag set
NAME                      READY     STATUS    RESTARTS   AGE
docker-registry-1-h7etw   1/1       Running   1          2h
router-1-uv0f9            1/1       Running   1          2h

$kubectl get pods --timeout=1ms
Unable to connect to the server: net/http: request canceled while
waiting for connection (Client.Timeout exceeded while awaiting headers)
```