Decoding BMP file created using GIMP

# Expected Behavior

I have a program that copies each pixel onto another picture with the same size:
The expected behavior is that the input.bmp should be cloned and saved as output.bmp

# Current Behavior

The output image is not exactly the input file.

# Failure Information (for bugs)

## Steps to Reproduce

```javascript
const Jimp = require('jimp');

async function program() {
const input = await Jimp.read('input.bmp');
const output = await Jimp.create(input.getWidth(), input.getHeight());

for (let y = 0; y < input.getHeight(); y++) {
for (let x = 0; x < input.getWidth(); x++) {
output.setPixelColor(input.getPixelColor(x, y), x, y);
}
}

await output.writeAsync('output.bmp');
}

program();
```

**Screenshots**

For some reasons, GitHub doesn't allow to upload BMP files. Here's the link to both files:

https://files.fm/u/g6htyvg4

## Context

- Jimp Version: v0.5.0
- Operating System: Linux Ubuntu 18.04.1
- Node version: v8.11.2