Number type support and type fix

Fixed:
`TypeError: 'undefined' is not an object (evaluating 'child.constructor')`
and
`TypeError: 'null' is not an object (evaluating 'child.constructor')`
when using array with undefined or null value.
It might be useful for conditionals.
For example:

```
div {}, [
  if (user.avatar) 
    img {src:user.avatar}
  span "Hallo, #{user.name}"
]
```

Also, added numbers support. 

```
i = 0
div {}, [
 i++
 i++
]
```