Add X-Forwarded-Proto header for ssl proxy (#128)
Add X-Forwarded-Proto header for ssl proxy (#128)

Backend application usualy use this header to determine protocal being
used at browser. Althought it's not part of the standard but it's a
defactor practise already.

* WikiPedia: https://en.wikipedia.org/wiki/List_of_HTTP_header_fields
* Ruby on Rails: https://github.com/josh/rack-ssl/blob/master/lib/rack/ssl.rb
typicode/hotel,typicode/hotel,typicode/hotel