Coltrane

- Add `order_by` to `directory_contents` templatetag.
- Fix `TOC` outputting 'None' when it should be `None`.

- Add `to_html` template tag. [37](https://github.com/adamghill/coltrane/pull/37) by [Tobi-De](https://github.com/Tobi-De)
- Breaking change: change `date` to `publish_date` in metadata. [39](https://github.com/adamghill/coltrane/pull/37) by [Tobi-De](https://github.com/Tobi-De)
- Breaking change: change `SITE` setting to `SITE_URL`.
- Automatically add `verbatim` templatetag around code fences.

- Update project name to `coltrane`.

- Fix bug where templatetags could not be loaded when the base directory was ".".

- Add `request` to the template context when building static sites.

- Fix bug where static site path was incorrect.