subtle completed challenge button for courseware and add completionMessage to coursewares

models/Courseware.js

@@ -15,6 +15,7 @@ var coursewareSchema = new mongoose.Schema({
     description: Array,
     tests: Array,
     challengeSeed: Array,
+    completionMessage: String, // Congratulations! You've finished our HTML and CSS track!
     challengeType: Number // 0 = html, 1 = javascript only, 2 = video
 });