Fix CSS compression for new SASS compiler

Change-Id: Ib8775b7e5cef7e2fa4ed270fd96ff838210e6f24
diff --git a/Gruntfile.js b/Gruntfile.js
index dd59ac3..51965ac 100644
--- a/Gruntfile.js
+++ b/Gruntfile.js
@@ -79,6 +79,7 @@
         options: {
           implementation: sass,
           style: 'compressed',
+          outputStyle: 'compressed',
           sourceMap: true
         },
         files: {