Image size increases on quality reduction

Using jimp's quality method does not give a expected linear result. After passing the quality percentage above the range of 60-65, the image quality increases.

```js
const buffer = * JPEG image buffer *
console.log('Before Compression Size is ', Buffer.byteLength(buffer))
const data = await jimp.read(buffer).then(image => image.quality(65))
buffer = await new Promise((resolve, reject) => {
data.getBuffer((jimp.MIME_JPEG), (err, buff) => {
if (err) reject(err)
console.log('After compression Size is ', Buffer.byteLength(buff))
})
})
```

Results in:
```
Before Compression Size is: 429
After Compression, Size is 744
```