Changelog for Octree-0.6.0.0

-*-Changelog-*- 0.6.0.0 Apr 2018 * Switched 3D vectors to `linear`. * Added first benchmark. 0.5.4.4 Dec 2017 * Remove doctest since it is fragile (depends on markdown-unlit being on path.) 0.5.4.3 Nov 2017 * Relax deps for GHC 8.2 0.5.4.3 May 2016 * Relax base dependency for GHC 8.0 (and base 4.9) 0.5.4.2 Apr 2014 * Passes GHC 7.10 RC Dec 22 2014 build. 0.5.4.1 Apr 2014 * Bump up upper bounds for GHC 7.10 0.5.3 Apr 2014 * Switched to automatically derived Functor, Foldable, Traversable