Rack env.keys

### Before the Rails request
---
- SERVER_NAME
- PATH_INFO
- HTTP_ACCEPT_ENCODING
- HTTP_USER_AGENT
- rack.url_scheme
- rack.run_once
- rack.input
- SCRIPT_NAME
- SERVER_PROTOCOL
- HTTP_IF_NONE_MATCH
- HTTP_ACCEPT_LANGUAGE
- HTTP_CACHE_CONTROL
- HTTP_HOST
- rack.errors
- REMOTE_ADDR
- SERVER_SOFTWARE
- REQUEST_PATH
- HTTP_ACCEPT_CHARSET
- HTTP_COOKIE
- HTTP_VERSION
- rack.multithread
- rack.version
- REQUEST_URI
- rack.multiprocess
- SERVER_PORT
- rack.session.options
- GATEWAY_INTERFACE
- QUERY_STRING
- rack.session
- HTTP_ACCEPT
- HTTP_CONNECTION
- REQUEST_METHOD


### After a Rails request
--- 
- action_controller.rescue.request
- SERVER_NAME
- rack.request.cookie_hash
- PATH_INFO
- HTTP_ACCEPT_ENCODING
- HTTP_USER_AGENT
- rack.url_scheme
- rack.run_once
- rack.input
- action_controller.request.request_parameters
- SCRIPT_NAME
- SERVER_PROTOCOL
- HTTP_ACCEPT_LANGUAGE
- HTTP_CACHE_CONTROL
- HTTP_HOST
- rack.errors
- REMOTE_ADDR
- SERVER_SOFTWARE
- REQUEST_PATH
- rack.request.cookie_string
- rack.request.query_hash
- HTTP_ACCEPT_CHARSET
- HTTP_COOKIE
- HTTP_VERSION
- rack.multithread
- rack.version
- action_controller.request.path_parameters
- REQUEST_URI
- rack.multiprocess
- SERVER_PORT
- rack.request.query_string
- action_controller.rescue.response
- rack.session.options
- GATEWAY_INTERFACE
- QUERY_STRING
- action_controller.request.query_parameters
- rack.session
- HTTP_ACCEPT
- HTTP_CONNECTION
- REQUEST_METHOD