* Only add `!` to selector class matching template candidate
Fixes#7226.
Before this PR, if you had a class like:
```css
.one .two {
background: black
}
```
...and then used `!one` in your template, the generated CSS would be this:
```css
.\!one .\!two {
background: black !important
}
```
This would cause the styles to not be applied unless you also added `!` to the beginning of other classes in the template that are part of this selector.
This PR makes sure that other classes in the selector aren't mistakenly prefixed with `!`, so that you can add `!` to only one of the classes in your template and get the expected result.
* Update CHANGELOG
* move `./tests/jit` to `./tests`
* make tests consistent
Abstracted a `run` function and some syntax highlighting helpers for
`html`, `css` and `javascript`.
