fixed #90

Not yet tested.
An example for the issue #87
Improvement of lazy load errors handling (issue #87)
Update CHANGELOG.md
Update CHANGELOG.md
Merge branch 'master' of https://github.com/mar10/fancytree
Merge pull request #91 from Koloto/loaderrors

Improvement of lazy load errors handling (issue #87)
Looks good, seems you have grokked deferreds better than me ;-)
Merge branch 'master' of https://github.com/mar10/fancytree