Support --ssh-command option

Adds the ability to specify the path or command used with ssh subcommand (eg, for mosh).

Support STDIN

Adds support for reading hosts from STDIN.

ssh-docker support

Changes:

• Adds an 'ssh-docker' subcommand to connect to docker hosts over SSH.
• Adds test cases.
• Improves defaults.

Support docker and docker-compose

0.4

Updates package info.