Add OWNERS; upgrade to 0.5.15

Test: make
Change-Id: Iaaf92cd0330ed273dbb6743c42848257d88b2341
diff --git a/METADATA b/METADATA
index f5a6faa..1b6ac6b 100644
--- a/METADATA
+++ b/METADATA
@@ -1,7 +1,5 @@
 name: "proc-macro-hack"
-description:
-    "Procedural macros in expression position"
-
+description: "Procedural macros in expression position"
 third_party {
   url {
     type: HOMEPAGE
@@ -11,7 +9,11 @@
     type: GIT
     value: "https://github.com/dtolnay/proc-macro-hack"
   }
-  version: "0.5.12"
-  last_upgrade_date { year: 2020 month: 3 day: 19 }
+  version: "0.5.15"
   license_type: NOTICE
+  last_upgrade_date {
+    year: 2020
+    month: 4
+    day: 17
+  }
 }