Closes #733

Closes #766

Closes #719

* Allow ignored_content to support markdown files

* Add test for markdown supported ignored_content

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).

Closes #756

* Set up CI with Azure Pipelines

[skip ci]

* Remove other CI + remove newline in anchor link tpl

* Some more Windows specific changes

Closes #752

Closes #726

Part fix of #742

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.

Closes #745

* Add hard_link_static config option.

* Copy or hardlink file depending on an argument.

Modify the call sites for `copy_file` to account for the extra argument.

* Plug the config setting through to copy_file.

Don't apply the config option to theme's static directory.

* Update documentation.

* Backticks make no sense in this comment.

* Addressing PR comments.

* Be consistent with argument naming.

Closes https://github.com/getzola/zola/issues/732

* Add --open flag to serve command, to open URL in default browser

* Mention serve --open flag in CLI documentation

Closes #722

Closes #727

* Update cli-usage.md

* clarify that it's only the links from markdown files that are being checked;

Signed-off-by: Igor Gnatenko <i.gnatenko.brain@gmail.com>

It looks like two links on this page didn't get updated with the change from `./` to `@/` in ec61a57.

Simplify yes/ehh/no links in README.md

0.8.0