Remove unsafe code

[bstrie]

For peace of mind it would be nice if steward was free of unsafe code. Currently it looks like there are a few unsafe blocks lying around doing transmutes, and if those are just there for performance then 1) figure out whether or not the performance of those bits of code actually matters, and 2) figure out if we can't defer that unsafe code to some more standard/tested library.

[rjzak]

I took a look at safe_transmute, but, despite it's name, it's not safe. We'll probably need to iterate through bytes and create structs/arrays manually.