Add ruby-head, fix allow_failures syntax, try to get rbx working

.travis.yml

@@ -6,10 +6,12 @@ rvm:
   - 1.9.3
   - 2.0.0
   - 2.1.0
+  - ruby-head
   - rbx
   - jruby-19mode
 matrix:
+  fast_finish: true
   allow_failures:
-    - jruby-19mode
-    - rbx
+    - rvm: jruby-19mode
+    - rvm: rbx
 

Gemfile

@@ -10,3 +10,8 @@ gem "rack"
 gem 'minitest', '~> 4.0'
 
 gem "jruby-openssl", :platform => "jruby"
+
+platforms :rbx do
+  gem 'rubysl', '~> 2.0'
+end
+