fix streaming
make Padrino server threaded in development if possible
Fix Padrino::Mailer::Mime.mime_type
Merge pull request #1697 from tyabe/fix_mime_type

Fix Padrino::Mailer::Mime.mime_type
Refactored cache_key to show the key in the logger if you use a Proc to
calculate it.
Merge pull request #1698 from padrino/refactor-route-cache-key

Log cache_key when using a Proc