Remove unbinding before removing listeners refactored

[seva-ask]

Refactoring of #317

[stephanenicolas]

Thx. I follow up.

[stephanenicolas]

@seva-ask . Would you mind patching the issue on travis (finbugs synchronization inconsistency).

No need to re-open a new PR each time. Just

• code,
• push on the same branch as much as you want to trigger the build on travis
• when it passes, squash your commits
• push --force on your remote and it will trigger the build one last time with a single commit.

Then tell me to review and merge ;)

[stephanenicolas]

Oh, and don't forget to rebase from current master, in case some recent commit changed anything regarding your patch.

[seva-ask]

I've done what you asked me.
I fixed real warnings from checkstyle and findbugs that failed the build.
But build is sometimes failed on one of the platforms because of network reasons, you can see it in logs. I don't know how to fix it, maybe somewhere timeout settings exist.
Please review the result.

[stephanenicolas]

Thx for this fix. It was really clear and easy to merge.

[seva-ask]

Thank you. I didn't know about squash, it's useful and interesting.