Browserify + watchify + babelify. Increase a time of calling and number of times

Hello.

I have some problam with browserify.

```
const appBundle = browserify({
entries: config.client.src.appModule, // main js file
debug: true,
packageCache: {},
cache: {}
}).transform(babelify, {only: './src/client'});

const b = watchify(appBundle);

function rebundle(bundler) {
return bundler
.bundle()
.on('error', function (err) {
gutil.log('Browserify error: ' + gutil.colors.red(err.message));
})
.pipe(source('app.js'))
.pipe(gulp.dest('./dist'));
}

gulp.task('watchify', function () {
rebundle(b);

b.on('update', function () {
rebundle(b)
});
b.on('log', gutil.log); // output build logs to terminal
});

gulp.task('browserify', ['jshint'], function () {
rebundle(appBundle);
});});
```

If use watchify i have after each reload increase the time of reloading and increasing repeating of calling transform.