Update dependencies

Author: zachleat

package.json

@@ -36,11 +36,11 @@
     "compatibility": ">=0.11"
   },
   "devDependencies": {
-    "ava": "^3.15.0"
+    "ava": "^4.3.0"
   },
   "dependencies": {
-    "debug": "^4.3.1",
-    "posthtml": "^0.15.1",
+    "debug": "^4.3.4",
+    "posthtml": "^0.16.6",
     "posthtml-urls": "1.0.0"
   }
 }