function checkImports(path, fn) {
  var nodes = imports[path];
  if (!nodes) return fn();
  if (!nodes.length) return fn();

  var pending = nodes.length
    , changed = [];

  nodes.forEach(function(imported){
    fs.stat(imported.path, function(err, stat){
      // error or newer mtime
      if (err || !imported.mtime || stat.mtime > imported.mtime) {
        changed.push(imported.path);
      }
      --pending || fn(changed);
    });
  });
}
Check `path`'s imports to see if they have been altered.

@param {String} path
@param {Function} fn
@api private