Add heapify function to binary heap

src/backing/pure/mod.rs

@@ -2,7 +2,7 @@
 pub mod binary_heap;
 
 /// A data structure usable for backing a "pure" queue
-pub trait PureBacking<T: Ord> {
+pub trait PureBacking<T: Ord>: FromIterator<T> {
     /// Instantiates a new data structure
     fn new() -> Self;
     /// Places an item into the queue