Merge pull request #2 from ncreuschling/define-required-ruby-version

define required Ruby version ~> 2.1

Author: websi

dkdeploy-php.gemspec

@@ -12,6 +12,7 @@ Gem::Specification.new do |spec|
   spec.description   = 'dkd PHP deployment tasks and strategies'
   spec.summary       = 'dkd php deployment tasks and strategies'
   spec.homepage      = 'https://github.com/dkdeploy/dkdeploy-php'
+  spec.required_ruby_version = '~> 2.1'
 
   spec.files         = `git ls-files`.split($/)
   spec.executables   = spec.files.grep(%r{^bin\/}) { |f| File.basename(f) }