Larger (bytes) processed file than original

# Expected Behavior

I expect the processed file size to be less than the original

# Current Behavior

The processed file size is greater than the original

# Failure Information (for bugs)

Even with `.quality(75)` and in some cases a smaller size then the original, the processed file is larger in bytes

```js
jimp.read("src/path/to/image.jpg", (err, file) => {
if (err) {
console.log(err);
} else {
file.resize(400, jimp.AUTO)
.quality(75)
.write("public/path/to/image.jpg");
}
});
```

- Jimp Version: latest
- Operating System: Mac
- Node version: 12