Bugfix: ssh.run(tuple) => error

Otherwise throws this

```py
  File "/home/user/pwntools/pwnlib/tubes/ssh.py", line 17, in __init__
    h = log.waitfor('Opening new channel: %r' % (process or 'shell'), log_level = self.log_level)
TypeError: not all arguments converted during string formatting
```
Merge pull request #75 from zachriggle/patch-2

Bugfix: ssh.run(tuple) => error