[conformal/btcutil] 818032: Add quick overview about addresses to doc.go.

[Dave Collins]

  Branch: refs/heads/master
  Home:   https://github.com/conformal/btcutil
  Commit: 8180321217893f64bd8b108ed00a2dd82a796ed5
      
https://github.com/conformal/btcutil/commit/8180321217893f64bd8b108ed00a2dd82a796ed5
  Author: Dave Collins <da...@conformal.com>
  Date:   2014-12-22 (Mon, 22 Dec 2014)

  Changed paths:
    M doc.go

  Log Message:
  -----------
  Add quick overview about addresses to doc.go.

Closes #4.