interceptors idea

[devmondo]

Hi,

this is such an amazing library, thank you very much for bringing it to us.

i got one issue

let model = {
name:'mike'
}

expressions.parse(`name +family `).call(model);

the result is mike undefined.

now if we can have something to intercept before and after binding we can do wild stuff, for example checking if model above has property 'family', if not we can replace undefined properties with empty string and warn developer through console log instead of showing undefined in the result.

thanks in advanced.