Revert "Merge pull request #87 from humanmade/rm-dead-code-87"

This reverts commit 39ceee2bf92e9fa6fa24b324b7bec92cf492f730, reversing
changes made to e5bf42d8043c56c5b12434e41428f10370730fa2.
Sign the request with a nonce so the endpoint can't be abused willy-nilly
Merge pull request #115 from humanmade/fix-size-estimate-115

File size calculating is borked entirely