v 2.5.0. Changed #iterate internals.
Moved #iterate single element eviction, to full queue flush after iteration completion.
Previous method is not accurate. I can't shift head on every function call, because the current element could be not the head element.

On branch master
modified:   Readme.md
modified:   lib/train.js
modified:   package.json
modified:   test/iterate-with-eviction-test.js