Restrict amber version as well.

bower.json

@@ -24,7 +24,7 @@
   ],
   "private": false,
   "dependencies": {
-    "amber": ">0.18.1",
+    "amber": ">0.18.1 <0.20.0",
     "amber-contrib-jquery": ">=0.2.0 <0.4.0"
   },
   "devDependencies": {