Allow wrapping function like `mem` does

Instead of passing a function to immediately call it, I'd like to wrap a function to be used later. From:

```js
function runMeNow() {}
function init() {
	pRetry(runMeNow, {
		bigOptionsObject
	}).then(console.log)
}

init();
```

to:


```js
const runMeRetried = pRetry.wrap(runMeNow, {
	bigOptionsObject
});
function init() {
	runMeRetried.then(console.log)
}

init();
```
