To override all child pages

Closes #397
Tests from PR #434

Closes #413
Closes #408

Fixes https://github.com/Keats/gutenberg/issues/510. Well, should help with it.

Fix #396

Fix #490

Closes #485

Local CSV/TOML/JSON loading Tera function

Close #446
Close #260
Close #478
Close #284
Close #480

Switch to an `Option<usize>` for the serialized value of `rss_items`.
This lets us just set a blank value in the configuration and thereby
include *all* items.

This is a backwards-compatible change; it does not affect the behavior
of existing configurations.

Fixes #468. Closes #471.

Fix #122

This allow to use base_url in robots.txt, to reference a sitemap for
example.

- unless forced, only use colors in tty
- support CLICOLOR and NO_COLOR vars
- switch to termcolor crate to handle output coloring

Also fix tests

Close #367, #372

I love the new support for custom taxonomies! I got a little thrown off when updating my site, though, as the docs didn't specify how the page would expose the taxonomies to the template. Wasn't too hard to figure it out, but I figured I'd save the next person who tries it the effort :)