Add ability to have post request filters

[emptyflash]

This includes coming up with a was to show where the request gets forwarded. Initial thought is something like:

["Plug1", "Plug2", "$", "PostPlug1", "PostPlug2"]
                    ^--this is where the forward plug is called```

[kentongray]

when you say post do you mean post method or after request (response)? that should just be a different property on the config IMO

[kentongray]

or perhaps just a different (optional?) method on the plug?