Adds server executable, updates README & man page

Major
  - Adds crescent executable to repo and moves http.lua to /lib/crescent

Minor
  - Adds version flag "--version|-v" to command options.
  - Edits README 'Requirements' and 'Roadmap'.

Bugfix
  - Fixes incorrect require path for man page.
  - Fixes typos & incorrect command examples in man page.