Fix Issue 7287 - BinaryHeap example

Two changes:

1. Fixed the array in the final assert. Not sure where the original array came from -- not Intro to Algorithms, I checked my copy!
2. Moved to documented unit test so we make sure it actually passes.

https://d.puremagic.com/issues/show_bug.cgi?id=7287
Merge pull request #1931 from Poita/bug7287

Fix Issue 7287 - BinaryHeap example