* maybe_slugify() only does simple sanitation if config.slugify is false

* slugify is disabled by default, turn on for backwards-compatibility

* First docs changes for optional slugification

* Remove # from slugs but not &

* Add/fix tests for utf8 slugs

* Fix test sites for i18n slugs

* fix templates tests for i18n slugs

* Rename slugify setting to slugify_paths

* Default slugify_paths

* Update documentation for slugify_paths

* quasi_slugify removes ?, /, # and newlines

* Remove forbidden NTFS chars in quasi_slugify()

* Slugification forbidden chars can be configured

* Remove trailing dot/space in quasi_slugify

* Fix NTFS path sanitation

* Revert configurable slugification charset

* Remove \r for windows newlines and \t tabulations in quasi_slugify()

* Update docs for output paths

* Replace slugify with slugify_paths

* Fix test

* Default to not slugifying

* Move slugs utils to utils crate

* Use slugify_paths for anchors as well

* Add path to `TranslatedContent`

This makes it possible to retrieve the translated page through the `get_page` function.

* Use TranslatedContent::path field in test_site_i18n

Use it with the `get_page` function to get a reference to the page object.

Closes #366

* Compute canonical path before adjusting parent path

* Don't use adjusted `parent` to recalculate `canonical` in `find_language`

* Add regression tests

- Test for correct canonical field when calling `new_page`
- Test for correct canonical field after calling `find_language`

* Let toc is visable through Page & Section variables in templates

* Removed the current toc variable from page & section

* Bump pulldown_cmark to version 0.6.0

* Rename headers to headings

* fix the issue of generating the search index for multiple language

* updat docs for generating the search index for multiple language

* fix failed tests

* add tests for the search index of multiple language

Closes #733

Closes #766

These functions expect that file_path can have base_path stripped from
it, but during reloading they can be given relative paths.  Maybe this
behaviour varies between the notify backends?

This fixes two zola serve panics on FreeBSD (poll backend).

Clippy is returning some warnings.  Let's fix or explicitly ignore
them.  In particular:

- In `components/imageproc/src/lib.rs`, we implement `Hash` explicitly
  but derive `PartialEq`.  We need to maintain the property that two
  keys being equal implies the hashes of those two keys are equal.
  Our `Hash` implementations preserve this, so we'll explicitly ignore
  the warnings.

- In `components/site/src/lib.rs`, we were calling `.into()` on some
  values that are already of the correct type.

- In `components/site/src/lib.rs`, we were using `.map(|x| *x)` in
  iterator chains to remove a level of indirection; we can instead say
  `.copied()` (introduced in Rust v1.36) or `.cloned()`.  Using
  `.copied` here is better from a type-checking point of view, but
  we'll use `.cloned` for now as Rust v1.36 was only recently
  released.

- In `components/templates/src/filters.rs` and
  `components/utils/src/site.rs`, we were taking `HashMap`s as
  function arguments but not generically accepting alternate `Hasher`
  implementations.

- In `src/cmd/check.rs`, we use `env::current_dir()` as a default
  value, but our use of `unwrap_or` meant that we would always
  retrieve the current directory even when not needed.

- In `components/errors/src/lib.rs`, we can use `if let` rather than
  `match`.

- In `components/library/src/content/page.rs`, we can collapse a
  nested conditional into `else if let ...`.

- In `components/library/src/sorting.rs`, a function takes `&&Page`
  arguments.  Clippy warns about this for efficiency reasons, but
  we're doing it here to match a particular sorting API, so we'll
  explicitly ignore the warning.

* Add check subcommand

* Add some brief documentation for the check subcommand

* Start working on parallel link checks

* Check all external links in Site

* Return *all* dead links in site

Closes #674

To ensure we will get the right `content`
directory.
Fix #629

Closes #607

Only happens for sections with lang != default

trim_{start, end} is introduced in rust 1.30.0 and
trim_{left, right} is deprecated since 1.33.0.

Closes #576

Closes #537