fix Content-Type to same type as official repository

[mtanda]

I think the Content-Type should be same as official repository.
https://gist.github.com/mtanda/5d02c0b2b6a8f8abfd2bfe1ec519641d

The motivation to fix Content-Type is, I want to access S3 hosted repository from API Gateway.
https://docs.aws.amazon.com/apigateway/latest/developerguide/integrating-api-with-aws-services-s3.html

I'm not sure why charset=binary is set, but it cause error when I access S3 via API Gateway.
The error message is Charset is invalid or illegal.
When I remove charset=binary from Content-Type, I can access S3 repository.

[mtanda]

@krobertson I'm terribly sorry to bother you, would you check this?

[brandonryan]

I am having this issue too. Cant seem to get around it.