Edited per comment below (don't leave this on dev!!! but things are changing quickly):
iron-router: {
"git": "https://github.com/EventedMind/iron-router" ,
"branch": "dev"
}
}
Have you tried this syntax?
iron-router: {
"git": "https://github.com/EventedMind/iron-router/tree/dev" ,
"branch": "master"
}
}