Issue with dependency versions (net-ssh and net-scp versions are incompatible)

When I run `bundle update` I get:

```
Fetching net-ssh 7.0.1 (was 6.1.0)
Installing net-ssh 7.0.1 (was 6.1.0)
Fetching net-scp 1.2.1 (was 3.0.0)
Installing net-scp 1.2.1 (was 3.0.0)
```

As you can see there is a major downgrade of net-scp after the upgrade of net-ssh.

More info:

https://github.com/net-ssh/net-scp/issues/61
