Removing clj-time from Elasticsearch publisher

[frankitox]

Hi! I was just looking at the Elasticsearch publisher and realized it depends on clj-time which depends on joda-time. Would you be interested in a PR removing that dependency and using Java time? From what I could gather this will remove support for Java versions lower than 8.

[BrunoBonacci]

Hi @frankitox,

it sounds like a good idea!, looking at the clj-time usage there are two places where it is used (slack and elasticsearch) and a couple of other places where it is listed as a dependency but not used.
Not sure why it's there.
thx

[frankitox]

I just published a PR to remove the dep. Let me know if there's anything you'd like to change!