Fix invalid ssh URL for all languages.

The current version of this book specifies an invalid URL for ssh repos. Switching between ssh syntax and url syntax requires slightly more than just adding the 'ssh://' prefix - the delimiter between host and path changes from ':' to '/'.

This is a valid url:

    ssh://user@server/project.git

This is an invalid url which git (and most other tools) will reject:

    ssh://user@server:project.git