[FEATURE] Fail fast behaviour for SMTP validation layer as not required configurable option

[Vladislav Trotsenko]

New feature request checklist

• I have updated truemail to the latest version
• I have read the Contribution Guidelines
• I have read the documentation
• I have searched for existing GitHub issues

Feature description

This feature depends on issue #108. Implement ability to use fail fast behaviour for SMTP validation layer. It should be a configurable and not required option like in example below:

Truemail.configure do |config|
  config.smtp_fail_fast = true # by default it's equal to false
end

When smtp_fail_fast = true it means that truemail ends smtp validation session after first attempt on the first mx server in any fail cases (network connection/timeout error, smtp validation error). It should reduce total time of SMTP validation session up to 1 second.

[Vladislav Trotsenko]

In a latest release 🚀