I was experimenting with the warden stemcells and found that I could upload
a locally downloaded stemcell, but that neither of the following worked:

```
$ bosh upload stemcell
https://bosh.io/d/stemcells/bosh-warden-boshlite-ubuntu-trusty-go_agent

$ bosh upload stemcell
https://bosh.io/d/stemcells/bosh-warden-boshlite-ubuntu-trusty-go_agent?v=2776
```

Should we be able to upload the stemcells directly to BOSH lite with a URL?
I based what I was doing off here:

http://bosh.io/stemcells/bosh-warden-boshlite-ubuntu-trusty-go_agent