Clean up & clarify README

Strings are wrapped in quotes, links to other resources used
Refactor s3_dir resource to have default values for owner & group
Fix issue with mode attribute & integer/string conversion

* Implicit conversions do not happen as expected.
* Replace the default of `nil` with a reasonable default (conforms to Chef
default for `file`, `cookbook_file`, etc. resources)
* Update README to follow suit
Add Serverspec integration tests for Test Kitchen runs
Add note about et_fog to README
Clean up CHANGELOG
Bump to v1.1.0