Drop dependency on deprecated gulp-util (#31)

Closes #30

index.js

@@ -1,7 +1,7 @@
 'use strict';
 
 var csso        = require('csso'),
-    gutil       = require('gulp-util'),
+    PluginError = require('plugin-error'),
     Transform   = require('stream').Transform,
     applySourceMap = require('vinyl-sourcemaps-apply');
 
@@ -42,7 +42,7 @@ module.exports = function (options) {
                 error = processParseError(source, inputFile, error.parseError, error.message);
             }
 
-            cb(new gutil.PluginError('gulp-csso', error));
+            cb(new PluginError('gulp-csso', error));
         }
 
         if (file.isNull()) {

package.json

@@ -24,12 +24,13 @@
   ],
   "dependencies": {
     "csso": "^3.0.0",
-    "gulp-util": "^3.0.6",
+    "plugin-error": "^0.1.2",
     "vinyl-sourcemaps-apply": "^0.2.1"
   },
   "devDependencies": {
     "tap-spec": "^4.1.0",
-    "tape": "^4.2.1"
+    "tape": "^4.2.1",
+    "vinyl": "^2.1.0"
   },
   "main": "index.js"
 }

test.js

@@ -3,7 +3,7 @@
 var csso    = require('./'),
     test    = require('tape'),
     Stream  = require('stream'),
-    gutil   = require('gulp-util'),
+    Vinyl   = require('vinyl'),
     fs      = require('fs'),
 
     basestyle  = 'h1 { color: yellow; } \n h1 { font-size: 2em; }',
@@ -20,7 +20,7 @@ function readSourceMapTestFile(ext) {
 }
 
 function fixture (contents) {
-    return new gutil.File({
+    return new Vinyl({
         contents: contents,
         cwd: __dirname,
         base: __dirname,
@@ -29,7 +29,7 @@ function fixture (contents) {
 }
 
 function sourceMapFixture (contents, sourceMap) {
-    var file = new gutil.File({
+    var file = new Vinyl({
         contents: new Buffer(contents),
         cwd: __dirname,
         base: __dirname,
@@ -106,7 +106,7 @@ test('should throw an error in stream mode', function (t) {
 
     var stream = csso();
 
-    var file = fixture(new Stream());
+    var file = fixture(new Stream.Readable());
 
     var write = function () {
         stream.write(file);