Add some sources to the unsign method

src/lib/jar.js

@@ -12,7 +12,9 @@ var pako = require('pako');
  */
 var Jar = {
     unsign: function (value, callback) {
-        // Return the usable content portion of a signed, compressed cookie
+        // Return the usable content portion of a signed, compressed cookie generated by
+        // Django's signing module
+        // https://github.com/django/django/blob/stable/1.8.x/django/core/signing.py
         if (!value) return callback('No value to unsign');
         try {
             var b64Data = value.split(':')[0];
@@ -23,6 +25,8 @@ var Jar = {
             }
 
             // Django makes its base64 strings url safe by replacing + and / with - and _ respectively
+            // using base64.urlsafe_b64encode
+            // https://docs.python.org/2/library/base64.html#base64.b64encode
             b64Data = b64Data.replace(/[-_]/g, function (c) {return {'-':'+', '_':'/'}[c]; });
             var strData = atob(b64Data);