fixes #71 using string length when counting characters.

Also example with ASCII colors added.
@jdan you're right! I just blindly copy-pasted the `Math.round(width * ratio)`
But it' s true that if desired width is say 6, then we should actually have 
```js
width = 6;
completeLength = Math.round(width * ratio) + 1;
complete = Array(completeLength).join("#"); // ######
```
to be fully accurate.

Another pull request?