Correctly quote CSS import path in test

Author: simonsmith

test/test.js

@@ -152,7 +152,7 @@ describe('suitcss', function() {
 
     describe('stylelint', function() {
       it('should check the input conforms to SUIT style rules', function(done) {
-        suitcss('@import ./stylelint.css', {
+        suitcss('@import "./stylelint.css"', {
           lint: true,
           root: 'test/fixtures',
           'postcss-reporter': {