Split out JRuby dependencies

sinatra-contrib/Gemfile

@@ -10,13 +10,21 @@ group :development, :test do
     gem 'rdoc'
   end
 
+  platform :jruby do
+    gem 'therubyrhino'
+  end
+
+  platform :jruby, :ruby do
+    gem 'slim', '2.1.0'
+  end
+
   platform :ruby do
     gem 'execjs', '2.0.0'
     gem 'nokogiri', '1.5.10'
     gem 'redcarpet', '2.3.0'
-    gem 'slim', '2.1.0'
     gem 'liquid', '2.6.1'
     gem 'yajl-ruby'
+    gem 'therubyracer'
   end
 
   gem 'multi_json'

sinatra-contrib/sinatra-contrib.gemspec

@@ -200,7 +200,6 @@ Gem::Specification.new do |s|
   s.add_development_dependency "slim"
   s.add_development_dependency "less"
   s.add_development_dependency "sass"
-  s.add_development_dependency "therubyracer"
   s.add_development_dependency "builder"
   s.add_development_dependency "liquid"
   s.add_development_dependency "redcarpet"