Replace Go implementation by a more naive one#59

I came across these benchmarks, and found the current Go implementation relatively hard to read. This (completely new) implementation aims to be better to read and maintain, with the following major differences: - Rename Node's X,Y to Value and Weight - Make methods of functions that operate on *Node - Concentrate complexity in the *Node methods The implementation seems to be a bit faster as well. PS: I've opted to replace the current `main.go` because this is also a 'naive' implementation using raw pointers. This makes the diff is a bit useless, sorry about that.