Adds Expires header for GET requests to Refile::App so responses could be cached by browser/proxies.
Merge pull request #60 from krists/refile-app-cahce-headers

Adds Expires header for GET requests to Refile::App
Add support for file type validations

closes #5
closes #44
Document that “Origin” header needs to be set in CORS config, closes #5
Allow HTTP connections when running tests with S3
Improve IO perf with IO.copy_stream and #send_file