Prepare release 3.7.0

CHANGELOG.md

 ## Changelog
 
+### 3.7.0
+  * Add support for Ubuntu 18.04 LTS (thanks @rogermartensson)
+  * Improved support for Debian 9 (thanks @carlgarner)
+  * Improvements to huntgroups (thanks @amateo)
+  * General bug fixes (thanks @infracaninophile, @coreone and @olivierlm))
+
 ### 3.6.0
   * Add support for Debian 9 (thanks @its-not-a-bug-its-a-feature)
 

metadata.json

 {
   "name": "jgazeley-freeradius",
-  "version": "3.6.0",
+  "version": "3.7.0",
   "author": "jgazeley",
   "summary": "Install and configure FreeRADIUS",
   "license": "Apache-2.0",
@@ -27,6 +27,12 @@
       "operatingsystemrelease": [
         "9"
       ]
+    },
+    {
+      "operatingsystem": "Ubuntu",
+      "operatingsystemrelease": [
+        "18.04"
+      ]
     }
   ],
   "dependencies": [