fix project's homepage references to CHANGELOG

[fgeorgatos]

@altercation an easy fix, the URLs happen to point to the unknown: https://ethanschoonover.com/solarized/CHANGELOG

[bakert]

This dead link is quite prominently featured high up on https://ethanschoonover.com/solarized/ in (bold, new paragraph) "See the changelog for what’s new in the most recent release."

The real link is https://ethanschoonover.com/solarized/CHANGELOG.mkd or https://github.com/altercation/solarized/blob/master/CHANGELOG.mkd although neither are up to date (last changed Apr 2011) so probably the real solution is to remove the whole emboldened paragraph.

(If you use the ethanschoonover.com link you may want to change the HTTP headers it is served with as it will download rather than display by default at least on my OSX/Chrome and OSX/Safari. It's served with Content-Type: application/octet-stream, probably because of the .mkd extension not being recognized?)