docs($exceptionHandler): add an example of overriding the handler

Closes #3816

src/ng/exceptionHandler.js

@@ -13,6 +13,20 @@
  * In unit tests, if `angular-mocks.js` is loaded, this service is overridden by
  * {@link ngMock.$exceptionHandler mock $exceptionHandler} which aids in testing.
  *
+ * ## Example:
+ * 
+ * <pre>
+ *   angular.module('exceptionOverride', []).factory('$exceptionHandler', function () {
+ *     return function (exception, cause) {
+ *       exception.message += ' (caused by "' + cause + '")';
+ *       throw exception;
+ *     };
+ *   });
+ * </pre>
+ * 
+ * This example will override the normal action of `$exceptionHandler`, to make angular
+ * exceptions fail hard when they happen, instead of just logging to the console.
+ *
  * @param {Error} exception Exception associated with the error.
  * @param {string=} cause optional information about the context in which
  *       the error was thrown.