Remove development dependencies from gemspec

Gemfile

@@ -1,3 +1,10 @@
 source 'http://rubygems.org'
 
+group :development do
+  gem 'rake'
+  gem 'rspec', '~> 3.0'
+  gem 'rspec-its'
+  gem 'rubocop'
+end
+
 gemspec

websocket.gemspec

@@ -18,9 +18,4 @@ Gem::Specification.new do |s|
   s.test_files    = `git ls-files -- {test,spec,features}/*`.split("\n")
   s.executables   = `git ls-files -- bin/*`.split("\n").map { |f| File.basename(f) }
   s.require_paths = ['lib']
-
-  s.add_development_dependency 'rake'
-  s.add_development_dependency 'rspec', '~> 3.0'
-  s.add_development_dependency 'rspec-its'
-  s.add_development_dependency 'rubocop'
 end