use pessimistic version constraint

- this is compatible with gem versions from 11.6.0 with minimal
  changes.
- mixlib-shellout differs in windows-versus-unix due to version pinning
  in windows-pr picking up old mixlib-shellout on windows, this is
  not fixed, and left similar to 11.6.0
- gem versions should be levelled up for 11.8.x and beyond
- newly built 11.6.0 will pick up new mixlib-config 2.0 which is
  a delta from the downloadable omnibus builds, 11.6.2 will not
  pick up mixlib-config 2.0

version bumping and docs for 10.28.2

Bump version number to 10.28.0 for release.

Bump version for RC.

Tag for release 11.6.0.hotfix.1

Release 11.6.0

Full Release Notes: https://github.com/opscode/chef-docs/blob/584310c31f4b7171a5bdf7c23c34c260e7a01a71/chef_master/source/release_notes.rst

Bump up version for RC.

Dev Version 11.8.0 Alpha 0

Bump the version number for RC.

Bumping the version number for the release candidate.