use triple-quoted strings to avoid backslashes

This should really read

```javascript
return Object.prototype.hasOwnProperty.call(value, prop);
```

as the object may have an own property named `hasOwnProperty`. For example:

```
> var o = {}
undefined
> o.hasOwnProperty('x')
false
> o.hasOwnProperty = 42
42
> o.hasOwnProperty('x')
TypeError: Property 'hasOwnProperty' of object #<Object> is not a function
> Object.prototype.hasOwnProperty.call(o, 'x')
false
```