Define if `dir` is a Epm repository

@param {String} dir
function isRepoSync(dir){
  var dirs

  if (dir instanceof Array){
    dirs = dir
  } else {
    dirs = getDirectoriesSync(dir)
  }

  var res = dirs.filter(function(name){ 
    return name.match(/\.epm/ig)
  });
  return res.length > 0;
}