Fix Rubinius by adding newly required gems, updating label in .travis.yml

.travis.yml

@@ -4,7 +4,7 @@ rvm:
   - 1.9.3
   - 2.0.0
   - ruby-head
-  - rbx-19mode
+  - rbx
 matrix:
   include:
   - rvm: jruby-19mode

Gemfile

@@ -1,5 +1,14 @@
 source 'https://rubygems.org'
 
+
+platforms :rbx do
+  gem 'rubysl', '~> 2.0'
+  gem 'rubysl-test-unit'
+  gem 'rubinius-developer_tools'
+  gem 'json'
+end
+
+
 gemspec
 gem 'rake'
 gem 'coveralls', :require => false