Update cucumber

cucumber 4.0.0 is not aware of breaking changes in diff-lcs 1.4.3, so
excluding it

cucumber 4.0.0 would run on Ruby 2.3, 2.4 and JRuby 9.1

Author: pirj

cucumber.yml

@@ -1,2 +1,2 @@
-default: --require features --tags ~@wip features --format progress
+default: --require features --tags 'not @wip' features --format progress
 wip: --require features --tags @wip:3 --wip features

rspec-mocks.gemspec

@@ -46,7 +46,7 @@ Gem::Specification.new do |s|
   s.add_runtime_dependency "diff-lcs", ">= 1.4.4", "< 2.0"
 
   s.add_development_dependency 'rake',     '> 12.3.2'
-  s.add_development_dependency 'cucumber', '~> 1.3.15'
+  s.add_development_dependency 'cucumber', '>= 3.2', '!= 4.0.0', '< 8.0.0'
   s.add_development_dependency 'aruba',    '~> 0.14.10'
   s.add_development_dependency 'minitest', '~> 5.2'
 end