Release: 1.5.2, add release notes (#2965)

Prompted by the caddy import path changes; prepare a new release.
Signed-off-by: Miek Gieben <miek@miek.nl>

notes/coredns-1.5.2.md

++++
+title = "CoreDNS-1.5.2 Release"
+description = "CoreDNS-1.5.2 Release Notes."
+tags = ["Release", "1.5.2", "Notes"]
+release = "1.5.2"
+date = 2019-07-03T07:35:47+01:00
+author = "coredns"
++++
+
+The CoreDNS team has released
+[CoreDNS-1.5.2](https://github.com/coredns/coredns/releases/tag/v1.5.2).
+
+Small bugfixes and a change to Caddy's important path.
+
+# Plugins
+
+* For all plugins the `upstream` directive was removed from the documentation; it's still accepted
+  but is a noop.
+* The [*file*](/plugins/file) closes the connection after an AXFR. It also loads secondary zones
+  lazily on startup.
+
+## Brought to You By
+
+bcebere,
+JINMEI Tatuya,
+Miek Gieben,
+Timoses,
+Yong Tang.
+
+
+## Noteworthy Changes
+
+* plugin/file: close correctlty after AXFR (https://github.com/coredns/coredns/pull/2943)
+* plugin/file: load secondary zones lazily on startup (https://github.com/coredns/coredns/pull/2944)
+* build: Update Caddy to 1.0.1, and update import path (https://github.com/coredns/coredns/pull/2961)
+* plugins: set upstream unconditionally (https://github.com/coredns/coredns/pull/2956)
+* tls: hardening (https://github.com/coredns/coredns/pull/2938)