Use recent JRuby release for Travis CI

Our JRuby CI runs have been errorring due to what I think is an issue
with an older `jruby-openssl` version.

lib/gollum/app.rb

@@ -1,5 +1,4 @@
-# encoding: UTF-8
+# ~*~ encoding: utf-8 ~*~
-
 require 'cgi'
 require 'sinatra'
 require 'sinatra/namespace'
@@ -70,8 +69,6 @@ module Precious
     register Sinatra::Namespace
     include Precious::Helpers
     
-    Encoding.default_external = "UTF-8"
-
     dir = File.dirname(File.expand_path(__FILE__))
 
     set :sprockets, ::Precious::Assets.sprockets(dir)