Map support

Hi!
I implemented map support, which converts this:

```python
def inc(x):
  return x + 1

array = [1, 2, 3]
result = map(inc, array)
print(result)
```
Into this (as defined in [MDN](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/map)):
```javascript
var inc = function(x) {
    return (x + 1);
};
array = [1, 2, 3];
result = array.map(inc);
console.log(result);
```

Can you, please, review and merge it?