Akka version 2.3.3 => 2.3.4
Use sbt-rc 7be0ef2928241f9d13137c7cb90f1c30238f1d25

This one uses sbt-echo 0.1.4 which is not broken.
Fix stale template cache information

 * if the cache already existed, we didn't re-download when
   we changed the hash
 * IO.download was downloading a stale current.properties
   which it apparently cached someplace
Go to template cache a6a9b0e5bce3a86411aa515dae159e0a48369f49