bake: Tweaks to the `sitemap` processor. Add tests. * Now using a `PageIterator` to get the expected behaviour from a given page source, such as skipping taxonomy pages and such. * Fix formatting of priority. * Use the bake time for `lastmod` attribute.

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