Adding  timeout to Paramiko.

Adding a default 10 seconds timeout to Paramiko connect and exec_command.
Raise timeout exception for ssh commands.

If a command executed by paramiko takes more than 10 seconds to return,
raise a timeout exception. Also raise a timeout exception in case of
connection interruptions.
Merge pull request #303 from omaciel/timeout-paramiko

Adding  timeout to Paramiko.