fix(seed): Change schema so tests pass

This is just a quick fix for the issue with the schema differences
between curriculum and the main fCC repo brought up in
freeCodeCamp/curriculum#204. The changes to
the schema here bring it in line with the more recently changed schema
in curriculum, and `npm run test` pass with the curriculum NPM package
3.1.2.

seed/schema/challengeSchema.js

@@ -41,6 +41,7 @@ const schema = Joi.object().keys({
   isRequired: Joi.bool(),
   name: Joi.string(),
   order: Joi.number().options({ convert: false }),
+  releasedOn: Joi.string().allow(''),
   required: Joi.array().items(
     Joi.object().keys({
       link: Joi.string(),
@@ -69,7 +70,14 @@ const schema = Joi.object().keys({
   ),
   template: Joi.string(),
   time: Joi.string().allow(''),
-  title: Joi.string().required()
+  title: Joi.string().required(),
+  translations: Joi.object().pattern(
+    /\w+(-\w+)*/,
+    Joi.object().keys({
+      title: Joi.string(),
+      description: Joi.array().items(Joi.string().allow(''))
+    })
+  )
 });
 
 exports.validateChallenge = function validateChallenge(challenge) {