vecvec

This is a rust crate that provides a type VecVec<T> that emulates aspects of Vec<Vec<T>> using a single Vec<T> for storage. The main purpose is to support the swap-remove idiom. When repeatedly creating and dropping many objects, the swap-remove idiom can be used to eliminate most allocations. This does not work however if the stored objects themselves allocate, as happens with Vec<Vec<T>>.