Update to joda-time 2.3 (and tzdata 2013d)

$ jruby -ve 'require "rbconfig";
puts RbConfig::CONFIG["joda-time.version"];
puts RbConfig::CONFIG["tzdata.version"]'
jruby 1.7.5.dev (1.9.3p392) 2013-09-02 ba28553 on Java HotSpot(TM) 64-Bit Server VM 1.7.0_25-b15 [darwin-x86_64]
2.3
2013d
Merge branch 'master' of jruby.org:jruby