Parser gets body from server process

The server is now sending the request body to the routing application.
It will always be arg[3]. Parser collects it.
Adds builder for POST requests

The POST request builder writes data to a new file.
Dispatcher routes POST requests

The Dispatcher accepts the request body and routes POST requests to the
new POST response builder.
Adds public/form to gitignore

Mock POST requests create a public/form file over and over. No need to
keep track of it in git.