Use native map when possible

Implemented on all modern browsers.

There is a small behavior difference between $.map and Array.prototype.map
but we don't rely on it.

(jQuery flatten arrays and filters null-like)

In our case there is ~ no performance benefit regarding speed.

But Warning, this is **not implemented on IE8**, only on IE9+,  what is our policy on IE ? 

Also, note to self, for compat table : 
http://caniuse.com/ and http://kangax.github.io/compat-table/es5/