[FEATURE] Better handling nil or non-string values?

[John Lemp]

New Issue 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

Issue Description

Calling Truemail.validate() or Truemail.valid?() with nil or non String values throws errors.

Complete output when running truemail, including the stack trace and command used

 Truemail.valid?(nil)
NoMethodError: undefined method `[]' for nil:NilClass
from .../gems/ruby-2.6.5/gems/truemail-1.9.1/lib/truemail/validator.rb:42:in `select_validation_type'

Took me a while to track down why my Validator was failing and seems somewhat unexpected result.

[Vladislav Trotsenko]

Hi, @duckworth! Thanks for your feedback. Follows the docs it's an expected behaviour for these cases. But I will add type-check handler in next release. Cheers!