Declare gem dependencies

capistrano-sneakers.gemspec

@@ -18,6 +18,11 @@ Gem::Specification.new do |spec|
   spec.test_files    = spec.files.grep(%r{^(test|spec|features)/})
   spec.require_paths = ["lib"]
 
+  spec.required_ruby_version = '>= 2.0.0'
+
+  spec.add_dependency 'capistrano', '>= 3.9.0'
+  spec.add_dependency 'sneakers'
+
   spec.add_development_dependency "bundler", "~> 1.7"
   spec.add_development_dependency "rake", "~> 10.0"
 end