Bump version to 0.6.6.

Hi,

This is just a request to bump up the version number to 0.6.6, which include the following changes https://github.com/markolson/chef-ssh/compare/52837a3f8c5e319d40f3dae917df329e6d95e7b3...master

Would you also mind creating two tags for `0.6.5` and `0.6.6`?
It can be done as follow:

```bash
git checkout 52837a3f
git tag 0.6.5
git checkout master 
git tag 0.6.6
git push --tags
```

This would be very helpful for people using dependency management such as Berkshelf and Librarian.

Cheers