protofile: use watchFile instead of watch

Using fs.watchFile seems to work on more cases than simply using watch.

Partially fixes issue discussed in #5

src/nodes/protofile.js

@@ -20,15 +20,13 @@ module.exports = function (RED) {
         if (protoFileNode.prototypes === undefined) return;
 
         try {
-            protoFileNode.protoFileWatcher = fs.watch(config.protopath, (eventType) => {
+            protoFileNode.protoFileWatcher = fs.watchFile(config.protopath, (eventType) => {
                 if (eventType === 'change') {
                     load();
                     protoFileNode.warn('Protobuf file changed on disk. Reloaded.');
                 }
             });
-            protoFileNode.on('close', () => {
-                protoFileNode.protoFileWatcher.close();
-            });
+            protoFileNode.on('close', () => fs.unwatchFile(config.protopath));
         }
         catch (error) {
             protoFileNode.error('Error when trying to watch the file on disk: ' + error);