add missing notready exception

core/sjcl.js

@@ -55,6 +55,12 @@ var sjcl = {
     bug: function(message) {
       this.toString = function() { return "BUG: "+this.message; };
       this.message = message;
+    },
+
+    /** @class Something isn't ready. */
+    notready: function(message) {
+      this.toString = function() { return "NOT READY: "+this.message; };
+      this.message = message;
     }
   }
 };