added article

test/data/schemas/article.js

@@ -0,0 +1,20 @@
+var Schema = require('mongoose').Schema;
+
+var ArticleSchema = new Schema({
+  title: {
+    type: String,
+    unique: true
+  },
+  body: String,
+  author: {
+    type: Schema.ObjectId,
+    ref: 'User',
+    required: true
+  },
+  created_at: {
+    type: Date,
+    'default': Date.now
+  }
+});
+
+module.exports = ArticleSchema;