For loop update

[jernejp21]

I have noticed that for loop syntax is not up to date with the latest zig.

Previous syntax for index of for loop elements: for (items) |item, index|

New syntax for index of for loop elements: for (items, 0..) |item, index|

I have created pull request #87.

I have already made pull request (which got merged) to cappy, which is dependent on apple pie.