[FEATURE] Render selector

[8ctopus]

This is a PR draft for selector tidying to transform this:

a>p {
    color: red;
}

a>p[title="hello>world"]>small {
    outline: 0;
}

into this:

a > p {
        color: red;
}

a > p[title="hello>world"] > small {
        outline: 0;
}

There are no specific tests yet, and there are improvements that can be made, I just want to get your approval before I polish things up.

[coveralls]

coverage: 68.833% (-0.4%) from 69.191%
when pulling 96889c3 on 8ctopus:render-selector
into 0ae1fde on MyIntervals:main.

[JakeQZ]

It would definitely be good to be able to render selectors minified.

However, as noted in #1398 (review), it is not straightforward to achieve that from the codebase as it stands.

I don't think the render() method should be responsible for reparsing the selector, which is already parsed by DeclarationBlock::parseSelector():

• render() should be able to simply output what it has according to the OutputFormat;
• adding separate parsing functionality here is duplicating functionality.

I think the problem that needs to be solved first is #1325 - i.e. how Selector is represented.

Sorry to be the bearer of bad news, but I think there's quite a bit of initial refactoring needed so that we can have a nice clean solution to this.

If you have any thoughts on solving #1325, they would be very welcome - thanks :) <3