New "for loop" features

I kept hating the fact that I had to define an old school while loop:

```
i = 0
while i <= 3
   log i
   i += 1
```

So, instead I created another statement which helps with this:

```
for i in 0 to 3
   log i
```

I know it doesn't save a lot of code or anything, but it just seemed more readable and easier to write.

Also, I was having a hard time understanding the grammar and generator (since I am new to these kind of projects) so my code might not be totally correct. Definitely might need some refactoring...