Fixed wrong argument in readme and added note on Amazon ES publisher.

[Lirt]

Just small update to README.

I mentioned that argument --zone is not working, there is only defined argument --zones.

And I added one note on using AWS ElasticSearch Publisher from, where port 9200 is closed and only accessible port is 80.
https://forums.aws.amazon.com/thread.jspa?messageID=681938

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[Lirt]

I signed it!

[googlebot]

CLAs look good, thanks!

[gareth-ferneyhough]

Thanks, LGTM.