Added implementation of pairing heap.
PairingHeap is tested and working. Also included are two initial testing suites: PairingHeapTest was made to test correctness. It's not neat, and about to be deleted. PairingHeapAnalysisTest was made to test efficiency.
Also made a fix to IdentityHashSet (don't know how that ever worked). Disabled the previous test suites in the project so they don't get repeated each time I test something with JUnit.