Templated map() function

Hello !

Apologies if this is a duplicate, but I couldn't find any previous discussions on github about it.

Is there a reason why map() isn't templated to provide maximum awesomeness??

Something as simple as this, would get rid of surprises when trying to use map() to scale to [0,1]:

```
template
T map(T x, T in_min, T in_max, T out_min, T out_max)
{
return (x - in_min) * (out_max - out_min) / (in_max - in_min) + out_min;
}
```