Investigate memory allocation/deallocation alternatives for wasmer

[ThetaSinner]

See #109 (comment)

Trying to use vectors for allocation and deallocation is risky because it depends on the internals of vector and how it chooses to do allocation. Is there an allocator we could use which hides some of these details? Or possibly just use layout/alloc/dealloc from the stdlib to more directly manage memory. Arrays allocated with alloc can still be wrapped in a slice or vector to be read.