Panicking tasks should abort process if not handled

RFC for issue opened here: https://github.com/rust-lang/rust/issues/19610

http://doc.rust-lang.org/std/sync/struct.Mutex.html

> In order to prevent access to otherwise invalid data, each mutex will propagate any panics which occur while the lock is held. Once a thread has panicked while holding the lock, then all other threads will immediately panic as well once they hold the lock.