Upload files directly to S3

[deoates]

I ended up using the dropzone JS library (http://dropzonejs.com) for file upload on the client. It sounds like we can hook it up to upload directly to S3:

http://docs.aws.amazon.com/AWSJavaScriptSDK/guide/browser-examples.html#Uploading_data_into_an_object

dropzone/dropzone#33

http://philfreo.com/blog/how-to-allow-direct-file-uploads-from-javascript-to-amazon-s3-signed-by-python/