Include numeric code points

Currently, the data includes things like:

```js
"unicode": "00021"
```

I.e. the Unicode code point values are included as hexadecimal digits in string form. Since they’re numbers, it’s much more convenient to expose them as such, i.e.:

```js
"unicode": 0x21
```

…which is equivalent to:

```js
"unicode": 33
```

That way, when the data is consumed, the `unicode` values can easily be turned into a string containing that symbol by using [ES6 `String.fromCodePoint(item.unicode)`](https://mths.be/fromcodepoint). (At the moment, you’d have to do something like `String.fromCodePoint(parseInt(item.unicode, 16))` to achieve the same result.)

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I would also propose renaming the vague `unicode` property to `code-point`.

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Do you want the file to remain valid JSON or not? If so, when we’ll need to use the code point values written as decimal numbers. If not, we can just use `module.exports = data;` and use `0xAB`-style hex integer literals (as in this patch). Let me know what you prefer and I’ll update the patch.