Can Jimp write a jpg file which exactly have the same color which I set?

# Expected Behavior

I used setPixelColor to operate the color of each pixels.

I used this to save the jpg file:

```javascript
picture.quality(100).writeAsync(path);
```

I wish that Jimp can write a jpg file which exactly have the same color which I set.

# Current Behavior

When I used getPixelColor to read the saved jpg,
I found that the colors are a little bit different with what I operated.

But this seems only effected with saving jpg.

After I saved the picture as bmp, I read the bmp file. I got the colors I wanted.

## Steps to Reproduce

1. Use Jimp.read to read the jpg file.
2. Use setPixelColor to edit a color of a pixel.
3. Use quality(100).writeAsync to save the file as a new jpg.
4. Use Jimp.read to read the new jpg file.
5. Use getPixelColor to get the color which I edited.
6. Compare the color with what I set before.
7. They are different a little.

## Context

- Jimp Version: 0.6.0
- Operating System: Windows 10 Pro 64bit
- Node version: 111.6.0

So, may I save the color into jpg strictly as what I want?

Thank you for checking this.

## Failure Logs

Nope.