1.2.0 makes multivalued params always required

[kke]

Setting required: false does not help:

require 'clamp'

Clamp do

  option ['--tag', '-t'], 'TAG', "Description", multivalued: true, required: false

  def execute
    puts tag_list.inspect
  end
end

$ ruby test_command.rb
ERROR: option '--tag' is required

See: 'test_command.rb --help'

Adding default: [] makes it fail with Specifying a :default value with :required doesn't make sense (ArgumentError).

[kke]

Probably caused by #81

[evgeni]

git bisect confirms afacbb1 is the first bad commit

commit afacbb1b9e63e3f7fb335218924288024733f43a
Author: Evgeni Golov <evgeni@golov.de>
Date:   Thu Dec 7 16:02:18 2017 +0100

    raise an error when a required, multivalued option is left blank
    
    checking for nil? returns false on an empty Array which is the default
    value for an multivalued option. also check for empty? in that case.

sorry about that

[evgeni]

#86 should fix this, @kke care to test?