Currently no, but you can inform us about bugs you found. If the bug can be reproduced, probably it will be fixed in the next release. You can also submit feature requests to the tracker.
Just submit the issue to the tracker. Don't forget to write detailed description of the bug and explain how to reproduce it. We'll include bug fix in one of next releases.
If you made a patch and / or improvement for the library, you can submit the source code to the tracker. We'll investigate it and include changes in the next release if it's reasonable. Note that in some cases your source code may be modified to meet the guide line of the project. It's better if you explain details of your patch in the meail message to avoid misunderstanding. If you do not allow any modifications of you code simply don't send the patch.