data: Fix problems with using non-existing metadata on a linked page. The page data wrapper now has supports for loader to raise a custom exception to declare that they can't return a value after all (this is especially useful for the wildcard loader). The returned value, if any, is also now cached properly.

{
  "name": "PieCrust",
  "version": "0.0.1",
  "private": "true",
  "dependencies": {
    "bootstrap": "~3.3.2"
  }
}