Use indexOf instead of includes

It should fix failing tests on circleci.

Author: znck

test/test.js

@@ -41,10 +41,10 @@ function test(name) {
             assert.equal(code.trim(), expected.trim(), 'should compile code correctly')
 
             // Check css output
-            if (['style', 'css-modules', 'css-modules-static', 'scss', 'pug', 'less'].includes(name)) {
+            if (['style', 'css-modules', 'css-modules-static', 'scss', 'pug', 'less'].indexOf(name) > -1) {
                 var css = read('expects/' + name + '.css')
                 assert.equal(css.trim(), actualCss.trim(), 'should output style tag content')
-            } else if (['no-css-extract'].includes(name)) {
+            } else if (['no-css-extract'].indexOf(name) > -1) {
                 assert.equal(undefined, actualCss, 'should ignore css()')
             } else {
                 assert.equal('', actualCss.trim(), 'should always call css()')