Refactors most controllers and directives into classes for more organized and maintainable code

app/assets/javascripts/models/noteHistoryEntry.js

@@ -0,0 +1,20 @@
+import { SFItemHistoryEntry } from 'snjs';
+
+export class NoteHistoryEntry extends SFItemHistoryEntry {
+
+  previewTitle() {
+    return this.item.updated_at.toLocaleString();
+  }
+
+  previewSubTitle() {
+    if(!this.hasPreviousEntry) {
+      return `${this.textCharDiffLength} characters loaded`
+    } else if(this.textCharDiffLength < 0) {
+      return `${this.textCharDiffLength * -1} characters removed`
+    } else if(this.textCharDiffLength > 0) {
+      return `${this.textCharDiffLength} characters added`
+    } else {
+      return "Title or metadata changed"
+    }
+  }
+}