Log Message:
security/ruby-sshkit: update to 1.18.0

## [1.18.0][] (2018-10-21)

  * [#435](https://github.com/capistrano/sshkit/pull/435): Consistent verbosity \ 
configuration #capture and #test methods - \ 
[@NikolayRys](https://github.com/NikolayRys)

## [1.17.0][] (2018-07-07)

  * [#430](https://github.com/capistrano/sshkit/pull/430): [Feature] Command \ 
Argument STDOUT/capistrano.log Hiding - \ 
[@NorseGaud](https://github.com/NorseGaud)

## [1.16.1][] (2018-05-20)

  * [#425](https://github.com/capistrano/sshkit/pull/425): Command#group \ 
incorrectly escapes double quotes, resulting in a a syntax error when specifying \ 
the group execution using `as`. This issue manifested when user command quotes \ 
changed from double quotes to single quotes. This fix removes the double quote \ 
escaping - [@pblesi](https://github.com/pblesi).