Minor cleanup, resolve some Clippy lints

[Diomendius]

I ran cargo clippy -- -W clippy::pedantic and fixed the issues it complained about that I thought were most reasonable. I also removed a redundant clone from watch.rs which Clippy surprisingly didn't complain about.

There were a few lints I decided against fixing, such as a |p| p.render() closure in handlebars_helpers.rs which would need to be expanded to the fully-qualified path handlebars::PathAndJson::render. There were a lot of instances of clippy::uninlined-format-args (fmt!("{} {}", x, y) → fmt!("{x} {y}")) which I didn't bother with, though if you prefer the inline style, you could run cargo clippy --fix -- -A clippy::all -W clippy::uninlined-format-args to auto-fix them.

I also noticed the crate is on edition = "2018". Changing this to edition = "2021" doesn't seem to require any other changes to the code, so it should be an easy change if you want to do that at some point.

[SuperCuber]

Looks good. I like the inline format args and the edition suggestions, could you add them to the PR?

[Diomendius]

I think I wrongly assumed you would be notified when I pushed commits, so this has sat open for longer than I expected. Sorry about that.

Anyway, I've revisited this, rebased to resolve the minor conflict in handlebars_helpers.rs, fixed some more lints and fixed a compile error I found along the way which would occur when running cargo test --no-default-features. I suppose the compile error is slightly out of scope for this PR, but the fix only adds two #[cfg] annotations, so I've included it with everything else.

This doesn't quite resolve everything that Clippy complains about with -W clippy::pedantic, but what remains is dubiously helpful. You can have a look yourself with cargo clippy --tests -- -W clippy::pedantic if you like.

[SuperCuber]

Looks great :D I commented on the .is_err() assert but I assume there might be more asserts like it, or .is_ok, .is_some etc. Please replace them with .unwrap and .unwrap_err :)

Then it's ready for merge

[Diomendius]

I actually couldn't find any other uses of .is_err(), .is_ok(), .is_some() or .is_none() in an assert, but I pushed a commit to fix the one you noticed.

And, since I happened to notice, for good measure I also renamed the config::tests module to test, since it was the only one not following that naming convention. I swear I didn't set out to make a bunch of single-character commits on purpose. 😅

[SuperCuber]

THanks for the contribution :D