Some fixes for scala-kinesis-enrich.

* Don't create a new geoIP obj every time we enrich an
  event, this opens the file every time and you can run
  out of file handles.
* Add ability to use IAM credentials (see #534)
* Don't wait for putResult, just log on complete (see #580)
* Use kinesis describe stream instead of liststreams + iterate (see #535)