updated make_link to use aws_config.s3_scheme instead of hardcoding 'htt...

Noticed that "http://" was hard coded into the make_link function and this was causing our page to complain about loading insecure content when using SSL. I've updated the method to instead load the s3_scheme from the erlcoud_aws.hrl file where it is defaulted to "https://" I was going to change the .hrl to be "http://" for backwards compatibility reasons but noticed that the method just below make_link (make_get_url) correctly uses the Config file so it just makes sense to default it to "https://"