Added initial support for a few conveniences

- options[:add_authorized_keys] option, when set to the name of a public
  key file, the contents of that key file will be added to
  authorized_keys when the conainer is created.
- options[:copy_on_create] - a list of files (based in home dir) which
  will be copied to the host on creation. Handy for .gitconfig,
  .ssh/config, etc

Version bump to 0.7.0