Feature: SCSS source map support

[SimonEast]

I've added support for SCSS source maps (as per Feature Request #13). This means that when you need to debug your SCSS in Chrome DevTools you can easily see which file the rules are coming from:

It required updating the SCSSPHP library to a later version and adding a new source map library.

Feedback and bug reports welcome.

(I needed to add a tiny micro-class for the purpose of overriding a third-party library function - it's currently at the bottom of of AutominService, let me know if there's a better place for it.)

Simon