Fix transform with serial: false

I am trying to use `serial: false` from dev branch and it only transform properly the first image. Here is the code I am using.

```javascript
FileAPI.upload('./upload', files, {
  serial: false,
  imageTransform: {
    type: 'image/jpeg',
    quality: 0.86, // jpeg quality
    maxWidth: 100
  },
  progress: function (evt){ /* ... */ },
  complete: function (err, xhr){ /* ... */ }
});
```

After take a look to the code I found this block:
```javascript
if( isOrignTrans ){
	// Convert to array for transform function
	trans = [trans];
}
```

It is inside of an each so we modify `trans` every iteration and finally we get something similar to `[[[trans]]]`, it causes transformation errors. I hope I fix it properly.