Bump to support B16

It still supports B15, but Extiverse won't show it :(

Author: davwheat

composer.json

@@ -7,7 +7,7 @@
   "type": "flarum-extension",
   "license": "MIT",
   "require": {
-    "flarum/core": ">=0.1.0-beta.15 <0.1.0-beta.17",
+    "flarum/core": ">=0.1.0-beta.16 <0.1.0-beta.17",
     "fof/extend": "^0.3.1"
   },
   "authors": [