Merge tag 'v3.4.0'

Dropzone.forElement throws an exception now instead of returning null if no Dropzone.
Merge tag 'v3.4.1'

Fixed Firefox progress update problems and travis.
Merge tag 'v3.5.0'

Added the addRemoveLinks option. Lots of improvements.
Merge tag 'v3.5.1'

Fixed travis tests
Merge remote-tracking branch 'origin/develop' into issue74
Folder upload support (for Chrome)

 - fixes #74
 - tested on Chrome 27 (on Mac)
Fix typo
Merge branch 'issue74' of https://github.com/gyuchang/dropzone into develop
Cleaned up folder handling and added download files.