Add strict type validator

Good catch. Any suggestions how to make it work?
The first thing that comes to mind is making number validation not so strict) It could be something like
```js
if(typeof value === 'string' && type === 'number') { value = JSON.parse(value); }
```
It would allow `'42', '-0.42', '1e6'`, but not `'042'` or `'42a'`. Does it look good?