Up version to 0.17.3.

Up version to 0.17.2. (mkdocs#1350)

Upped version to 0.17.1.

Version to 0.17.0

Also made a couple adjustments to "documented" Python versions.

Bump version to 0.16.3.

Version bump to 0.16.2

Bump the version and add release notes

Bumping the Mkdocs Version to roll a release

Merge pull request mkdocs#827 from d0ugal/master

Handle relative paths in symlinks

Bump version to 0.15.2