Version 1.7

This is one of the biggest releases of the Let's Encrypt controller so far!
The single most notable change is that the controller has been rewritten (or
rather "refactored") as a Kotlin application instead of the previous
"Spooky Java"-stack, but there are several other enhancements and fixes as
well.

Simply deploy the controller manifest to your cluster to get started.

---

Features:

• The controller has been re-written in Kotlin! Detailed information can be found
  in pull request #57 and issue #54
• Support for split-brain Route53 setups has been added by ignoring private zones
  during zone selection (see #61 and #64, thanks @itomaldonado!)
• The controller will now re-provision certificates if domains are removed from
  a certificate request.

Fixes and chores:

• All outdated dependencies have been bumped. Note: This has the minor effect
  that the created Secret-object no longer contains a field with only the
  intermediate certificates (previously the chain field).
  Due to changes in the acme4j library, both the chain and fullchain fields now
  contain a full certificate chain. The chain field will be deprecated in a future
  version.
• The MIT-license has been re-added to the project (thanks @ensonic for pointing it out!).
  All trees in this repository that do not have a LICENSE file can be assumed to be
  MIT-licensed, too.
• The build system used by this project is now Gradle, but this has no user-visible
  changes.

As always there have been some minor refactorings and fixes along the way.