Start working on v3.7

[rowanwins]

• add support for base64 images. resolves How can I manually add base64 strings in the dropzone? #543 and resolves Cannot display images correctly using manuallyAddFile()  #474
• add the accepted flag to manually added files. resolves getAcceptedFiles shows empty after manuallyAddFile #529
• Add support for uppercase filename previews
• remove use of deprecated lastModifiedDate. resolves TypeError: this.files[t].lastModifiedDate is undefined #482
• make manual thumbnail fit consistent but overridable via CSS. resolves How to resize preloaded images to fit the thumbnail size #455
• add new prop for Dropzone.confirm

Entirely overhaul S3 approach

• Ensure standard dropzone events are emitted, resolves Event "vdropzone-error" does not seem to fire with AWS #506
• Allows cancelling of uploads. resolves aws S3 upload continues after cancellation? #538 , resolves How to cancel uploading files to S3? #514

[fnagel]

Any chance to include the new "displayExistingFile" method? See #560