Thom van der Woude

Results 7 issues of Thom van der Woude

Addresses #3 by making it possible to specify whether diagonals are allowed, changing the generated node neighbors and heuristic accordingly

Currently a [binary heap](https://en.wikipedia.org/wiki/Binary_heap) is used. Alternatives include a [pairing heap](https://en.wikipedia.org/wiki/Pairing_heap) or a [radix heap](https://en.wikipedia.org/wiki/Radix_heap). This could bring insertion cost [down from Θ(log n) to Θ(1)](https://en.wikipedia.org/wiki/Pairing_heap#Summary_of_running_times)

enhancement

Closes #9