Changes since 1.4:

- Converted to automake/autoconf for configuration, which should make
  it easier to extend portability.

- Added support for checking multiple addresses in one invokation.

- Added support for reading addresses to check from standard input, by
  specifying an argument of '-'.

- Changed rbl.dorkslayers.com to relays.orbs.org, due to a change in
  management.
