remove support for chef handler logic magic

This was only to support Chef versions prior to 0.10.9 - this version is
far gone, and the method is generally simpler.
remove any integration-specific dependencies

These are no logner needed from version 5.x and higher.
replace tailor with rubocop
whitespace removal
update deprecated method call, styling
address StringLiterals [style]
update to testing

Gemfile updates, which versions to test on