Use proper "github.com" urls for importing cloud66 packages.

Otherwise, on a fresh clone and a `go get` will spit out the following errors:

```bash
cx (master) $ go get
package cloud66.com/cx/cloud66: unrecognized import path "cloud66.com/cx/cloud66"
package cloud66.com/cx/term: unrecognized import path "cloud66.com/cx/term"
```