Relax :application validator to allow hyphens
Relax :application validator to allow hyphens

Also improve the error message to explain what characters are allowed, and
include the offending value.

harrykiselev/capistrano,maliqq/capistrano,harrykiselev/capistrano,jdelStrother/capistrano,capistrano/capistrano,kirs/capistrano,kylerippey/capistrano,capistrano/capistrano,ngpestelos/capistrano,kirs/capistrano,maliqq/capistrano,ngpestelos/capistrano,jdelStrother/capistrano,kylerippey/capistrano