Always prevent default file drop action. Fixes #20
0.4.1
Take drag handle offset into account
0.4.2
Change acceptDrop signature to (item, e, isHandled, effect?)
0.5.0
Use Copy as drop effect for files
0.5.1
Update code and examples to React 0.12
0.6.0
Merge branch 'master' into experiments
Continue experimenting