fix(wording): clarify compass/scss feature prompt

- this better clarifies what experience the user can expect if they
answer yes to the compassBootstrap prompt, specifically that the .scss
(not .sass) version of bootstrap will be used
- aside: I waffled on whether to include `(requires Ruby)` at the tail
end of the message, but decided against it as the default error message
the user sees when they don't have ruby installed is pretty explicit.

Author: davemo

app/index.js

@@ -85,7 +85,7 @@ Generator.prototype.askForBootstrap = function askForBootstrap() {
   }, {
     type: 'confirm',
     name: 'compassBootstrap',
-    message: 'Would you like to use Twitter Bootstrap for Compass (as opposed to vanilla CSS)?',
+    message: 'Would you like to use the SCSS version of Twitter Bootstrap with the Compass CSS Authoring Framework?',
     default: true,
     when: function (props) {
       return props.bootstrap;