Don't put docs which are already in s3 through archive job

This fixes the bug we saw with 'RangeError: Maximum call stack size exceeded'
if lots of docs are already in s3 cb() gets called synchronously multiple times quickly
which can cause the execption. I am not sure where the recursion is, maybe inside async.

doing setImmediate(cb) also fixes the issue as I beilve it gives the
process chance to clear the stack. Similar to process.nextTick

Release version 0.1.4

Release version 0.1.3

Release version 0.1.2

Release version 0.1.0