Revert "Utilize __toString since that's kind of why that was implemented in the first place."

This reverts commit ed2fdcd4fa65c5d0d4960208841a21ec02541fa1.
Revert "SplObjectStorage implemented getHash in PHP >= 5.4.0. Implement temporary backwards compatability to support control of object hashes so we can easily fetch vertices by data."

This reverts commit 982828eecd019fd93ce3745db5a3326a42d0cf0a.
Merge branch 'master' into feature/v0.9

Conflicts:
	src/CentralDesktop/Graph/Graph.php
	src/CentralDesktop/Graph/VertexSet.php