use beeper module which checks TTY and adheres to --no-beep flag

https://github.com/sindresorhus/beeper

index.js

@@ -6,7 +6,7 @@ module.exports = {
   log: require('./lib/log'),
   template: require('./lib/template'),
   env: require('./lib/env'),
-  beep: require('./lib/beep'),
+  beep: require('beeper'),
   noop: require('./lib/noop'),
   isStream: require('./lib/isStream'),
   isBuffer: require('./lib/isBuffer'),
@@ -15,4 +15,4 @@ module.exports = {
   combine: require('./lib/combine'),
   buffer: require('./lib/buffer'),
   PluginError: require('./lib/PluginError')
-};
+};

package.json

@@ -5,6 +5,7 @@
   "repository": "wearefractal/gulp-util",
   "author": "Fractal <contact@wearefractal.com> (http://wearefractal.com/)",
   "dependencies": {
+    "beeper": "^1.0.0",
     "chalk": "^0.5.1",
     "dateformat": "^1.0.7-1.2.3",
     "lodash": "^2.4.1",