Add CORS headers?

[bhaugen]

See valueflows/valueflows#83

https://github.com/valueflows/linked-data-browser needs them for round tripping.

LDB is down right now, but running my Personator profile through raw worked worked:
http://dinosaur.is/linked-data-browser/?viewId=nodeList&focusId=https%3A%2F%2Frawgit.com%2Fbhaugen%2Fopen-data-self%2Fmaster%2Fdata.json
while this one didn't:
https://raw.githubusercontent.com/bhaugen/open-data-self/master/data.json

Error message:

Fetch API cannot load https://github.com/bhaugen/open-data-self/blob/master/data.json. No 'Access-Control-Allow-Origin' header is present on the requested resource. Origin 'http://dinosaur.is' is therefore not allowed access.