test(lint): add lint for synchronous randomBytes usage

.eslintrc

@@ -1,4 +1,6 @@
-extends: fxa/server
+plugins:
+  - fxa
+extends: plugin:fxa/server
 
 rules:
   handle-callback-err: 0

package.json

@@ -65,7 +65,7 @@
   },
   "devDependencies": {
     "commander": "2.9.0",
-    "eslint-config-fxa": "2.1.0",
+    "eslint-plugin-fxa": "git+https://github.com/mozilla/eslint-plugin-fxa#master",
     "fxa-auth-db-mysql": "git+https://github.com/mozilla/fxa-auth-db-mysql.git#master",
     "fxa-conventional-changelog": "1.1.0",
     "grunt": "1.0.1",

scripts/.eslintrc

@@ -1,5 +1,7 @@
 {
+  "plugins": ["fxa"],
   "rules": {
-    "no-console": 0
+    "no-console": 0,
+    "fxa/async-crypto-random": 0
   }
 }

test/.eslintrc

@@ -0,0 +1,6 @@
+plugins:
+  - fxa
+extends: ../.eslintrc
+
+rules:
+  fxa/async-crypto-random: 0