Implementing Vec -

# Example: Implementing Vec

To bring everything together, we're going to write `std::Vec` from scratch. Because all the best tools for writing unsafe code are unstable, this project will only work on nightly (as of Rust 1.9.0). With the exception of the allocator API, much of the unstable code we'll use is expected to be stabilized in a similar form as it is today.

However we will generally try to avoid unstable code where possible. In particular we won't use any intrinsics that could make a code a little bit nicer or efficient because intrinsics are permanently unstable. Although many intrinsics do become stabilized elsewhere (`std::ptr` and `std::mem` consist of many intrinsics).

Ultimately this means our implementation may not take advantage of all possible optimizations, though it will be by no means naive. We will definitely get into the weeds over nitty-gritty details, even when the problem doesn't really merit it.

You wanted advanced. We're gonna go advanced.