Improve CSS selector modification support

[o0101]

The issue is, there are some complex types of selectors that our simple selector parsing implementation (used to determine the proper insertion point for the unique class to scope the rule) will not work on.

It's an enhancement to be able to support these types as well.

[o0101]

For instance, we need to be able to handle (and currently I think we do not), the types of selectors illustrated by the following examples:

:matches(tagone, tagtwo, tagthree) { 
  /* we will incorrectly separate on the commas and spaces */
}
[attr="value" i] { 
  /* we will incorrectly insert on the first space before the i */
}
@directive keyword and (attribute: value) {
  selector {
    /* we will not modify 'selector' here because we ignore CSSRules without type == STYLE_RULE */
  }
}

[o0101]

Facing the issue of not working with media queries yet.

The holygrail layout component introduced in https://github.com/crislin2046/brutestrap/commit/510dbcbfb39e8c67bc395e6772b2900571556336

will not be responsive because the media rules set for it are ignored by C3S.