fix(wording): clarify compass/scss feature prompt

~~`(as opposed to vanilla CSS)?` seems to imply that the default would be vanilla CSS, so this changes that default to match that expectation.~~

~~The goal of this pull request is to try and better align `generator-angular` for cross platform support _as a default_, as it stands now if users don't take the time to read through the prompts, `generator-angular` sets up Compass/SASS by default on platforms where it is non-trivial to setup Ruby (lookin' at you, Windows) ;)~~

Updated to modify the wording of the compassBootstrap prompt to better describe the outcome of choosing `yes` to this prompt.