brew.sh: Add `ssh-copy-id`
brew.sh: Add `ssh-copy-id`

`ssh-copy-id` allows one to easily set up passwordless SSH connections on a new machine. It does this by copying over your pubic key and setting the correct permissions.

It becomes as simple as `ssh-copy-id user@hostname.example.com`. Probably safer than using manual or scripted methods.

Ref. http://askubuntu.com/a/4833/42234.

Closes #510.

troyxmccall/dotfiles,troyxmccall/dotfiles,troyxmccall/dotfiles