• Fix bug preventing persistent session expiration
  (persistent_client_expiration in vernemq.conf) from being executed.
• Make vmq-admin session show more robust when sessions are overloaded by
  limiting the time allowed to query each session. The default query timeout is
  100ms, but can be overriden using --rowtimeout=<TimeoutInMilliseconds>.
• Add support for Erlang/OTP20.
• Improve tracer usage text.
• Fix vmq_diversity memcached issue (#460).
• Fix RPM package issue preventing a clean upgrade.
• Fix code path bug related to upgrading plugins.
• Update plumtree with a fix to make the plumtree mailbox traversal
  measurement more accurate and therefore less spammy.