Counting sort

Counting sort: [https://en.wikipedia.org/wiki/Counting_sort](https://en.wikipedia.org/wiki/Counting_sort)

Given an array of N numbers where each number falls in the range [1-100,000], return the sorted array. Time complexity should be O(n).

Example:

```
vector<int> sort(vector<int> numbers) {
  // should return sorted array.
}
```

You can use any language you are comfortable with.