Fix open-ended dependencies

Author: pedrocarrico

fork_break.gemspec

@@ -18,6 +18,6 @@ Gem::Specification.new do |gem|
   gem.require_paths = ['lib']
   gem.version       = ForkBreak::VERSION
   gem.add_dependency 'fork', '= 1.0.1'
-  gem.add_development_dependency 'rspec', '>= 3.1.0'
-  gem.add_development_dependency 'rubocop', '>= 0.27.1'
+  gem.add_development_dependency 'rspec', '~> 3.1', '>= 3.1.0'
+  gem.add_development_dependency 'rubocop', '~> 0.27', '>= 0.27.1'
 end