Updated readme and added node 6 as test target

.travis.yml

@@ -1,6 +1,6 @@
 language: node_js
 node_js:
  - "4.0"
- - "5.0"
+ - "6.0"
 script: npm run test:coverage
 after_script: npm run coveralls

README.md

@@ -5,7 +5,20 @@ Like [freeport](https://libraries.io/npm/freeport) but with promises.
 
 ```javascript
 freeport()
-.then((port) => {
+.then(port => {
+  console.log(port)
+})
+```
+
+## Using other promise libraries
+
+By default we use the language-level `Promise` class, but if you want to use a different implementation, just pass it in as an argument:
+
+```javascript
+const bluebird = require('bluebird')
+
+freeport(bluebird)
+.then(port => {
   console.log(port)
 })
 ```

lib/freeport.js

@@ -1,9 +1,9 @@
-var net = require('net')
+const net = require('net')
 
-module.exports = (PromiseLibrary) => {
+module.exports = PromiseLibrary => {
   PromiseLibrary = PromiseLibrary || Promise
   return new PromiseLibrary((resolve, reject) => {
-    var server = net.createServer()
+    const server = net.createServer()
     var port = 0
 
     server.once('listening', () => {

test/freeport.js

@@ -1,20 +1,22 @@
-var freeport = require('../lib/freeport')
-var expect = require('chai').expect
-var describe = require('mocha').describe
-var it = require('mocha').it
+const freeport = require('../lib/freeport')
+const expect = require('chai').expect
+const describe = require('mocha').describe
+const it = require('mocha').it
 
 describe('freeport', () => {
   it('should find a free port', () => {
     return freeport()
-    .then((port) => {
+    .then(port => {
       expect(port).to.be.a('number')
       expect(port).to.not.equal(0)
     })
   })
+
   it('should work with a external promise library', () => {
-    var bluebird = require('bluebird')
+    const bluebird = require('bluebird')
+
     return freeport(bluebird)
-    .then((port) => {
+    .then(port => {
       expect(port).to.be.a('number')
       expect(port).to.not.equal(0)
     })