CyHeapQ - HeapQ in Cython

This module is an adaptation of merge, nlargest and nsmallest from the heapq module in Cython. This makes it just a tad bit faster.

x 1.5 for nlargest and nsmallest (given a particular micro benchnmark of course). x 3 for merge. nlargest performance is comparable with cytoolz.topk (but cyheapq also provides nsmallest). merge is around 8 times faster than cytoolz.merge_sorted. The microbenchmark used involves sifting / merging 10e6 random floats.