Restrict amber version as well.

bower.json

@@ -20,7 +20,7 @@
     ],
     "private": false,
     "dependencies": {
-        "amber": ">0.18.1",
+        "amber": ">0.18.1 <0.20.0",
         "amber-contrib-web": ">=0.4.0 <0.5.0",
         "jquery-ui": ">=1.9.2",
         "codemirror": "^5.10.0",