theme: provide some info on the SASS theming

- use bundles for using SASS v 3.4+
- README
- shell script

data/theme/Gemfile

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+gem "sass", "~> 3.4.0"

data/theme/README

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+Summary
+-------
+
+* Do not edit the CSS directly, edit the source SCSS files and process them with SASS (run 
+  `/.parse-sass.sh` when you have the required sofwtare installed, as described below)
+* To be able to use the lates/adequate version of sass, install ruby, gem, sass & bundle. 
+  On Fedora F20, this is done with `sudo dnf install rubygems && gem install bundle && bundle install`
+  from the same directory this README resides in.
+
+How to tweak the theme
+----------------------
+
+Adwaita is a complex theme, so to keep it maintainable it's written and processed in SASS, the
+generated CSS is then transformed into a gresource file during gtk build and used at runtime in a 
+non-legible or editable form.
+
+It is very likely your change will happen in the _common.scss file. That's where all the widget 
+selectors are defined. Here's a rundown of the "supporting" stylesheets, that are unlikely to be the 
+right place for a drive by stylesheet fix:
+
+_colors.scss        - global color definitions. We keep the number of defined colors to a necessary minimum, 
+                      most colors are derived form a handful of basics. It is an exact copy of the gtk+ 
+                      counterpart. Light theme is used for the classic theme and dark is for GNOME3 shell 
+                      default.
+
+_drawing.scss       - drawing helper mixings/functions to allow easier definition of widget drawing under
+                      specific context. This is why Adwaita isn't 15000 LOC.
+
+_common.scss        - actual definitions of style for each widget. This is where you are likely to add/remove
+                      your changes.
+                      
+You can read about SASS at http://sass-lang.com/documentation/. Once you make your changes to the
+_common.scss file, you can either run the ./parse-sass.sh script or keep SASS watching for changes as you
+edit. This is done by running `bundle exec sass --watch --sourcemap=none .` If sass is out of date, or is
+missing, you can install it with `bundle install`.

data/theme/parse-sass.sh

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+#!/usr/bin/bash
+
+bundle exec sass --update --sourcemap=none .