Have sass-cache in temp folder

.gitignore

@@ -1,3 +1,4 @@
 node_modules/
 npm-debug.log
 static/
+tmp/

Gruntfile.js

@@ -74,6 +74,7 @@ module.exports = function (grunt) {
         options: {
           sassDir: 'assets/style',
           cssDir: 'static/style',
+          cacheDir: 'tmp/sass-cache',
           importPath: ['vendor/normalize-scss']
         }
       }