Pull request for patch for Issue 187.

This patch modifies the following methods so that they update the updated_at timestamp:
- The Job.log method
- The Job.progress method
- The Job.attempt method
- The Job.state method

Consequently, the following methods will also exhibit the same behaviour:
- The Job.error method, because it uses the log method.
- The complete, failed, inactive, active, methods, because they use state method.

I hope this fix finds its way to the master branch soon.