done

* DONE split config from source code.
  config variables should be set in /etc/ddclient-http.conf
  and it can be sourced by the source code.

  move username, password, domain name, update URL to $HOME/.ddclient-httprc

  then source that at run time.

* DONE BUG when I just updated my domain. I do a dig, I get the old IP. 
  I try a new update. I get "nochg". I might get blocked if this happens
  often.

  extended crontab gap to 4 minutes. Since most Dynamic host has a TTL of 60s,
  this should be OK.