Extract getUsbEndpoints() to util.js. Use ES6 features in led_pwm.js

usb/util.js

@@ -1,4 +1,27 @@
+var usb = require('usb');
+
 exports = module.exports = {
+    getUsbEndpoints: function() {
+        var vid = 0x16d3;
+        var pid = 0x05ea;
+
+        var device = usb.findByIds(vid, pid);
+        device.open();
+
+        var usbInterface = device.interface(0);
+
+        // https://github.com/tessel/node-usb/issues/147
+        // The function 'isKernelDriverActive' is not available on Windows and not even needed.
+        if (process.platform !== 'win32' && usbInterface.isKernelDriverActive()) {
+            usbInterface.detachKernelDriver();
+        }
+        usbInterface.claim();
+
+        var endpointIn = usbInterface.endpoints[0];
+        var endpointOut = usbInterface.endpoints[1];
+        return [endpointIn, endpointOut];
+    },
+
     bufferToString: function(buffer) {
         var str = '';
         for (var i = 0; i < buffer.length; i++) {