Replaced all 'for' loops with Enumerable#each

[ndbroadbent]

Was reading a small discussion on r/ruby about for loops vs. Enumerable#each.

foo.each do |bar| is definitely the most common and preferred style, so I grepped the Rails codebase and replaced the 27 for loops that I found.

[spastorino]

Seems fine to me but please don't change the code under vendor

[ndbroadbent]

Fixed, sorry I missed that

[jeremy]

In most of these cases, for is easier to read than the #each equivalent.

No sense changing them wholesale because a Reddit thread says they're uncommon!

[spastorino]

I've applied the patch not because of Reddit thread, probably I should've commented my thoughts first :(.
I've applied it because I find the code better to read but if you don't like feel free to revert it

[ndbroadbent]

Thanks for the feedback. Now that I look at it again, I agree that for loops are easier to read when dealing with ranges.

Here's a pull request to revert to using for loops for ranges.