[conformal/btcutil] 5509c3: Add test coverage badge to README.md.

[Dave Collins]

  Branch: refs/heads/master
  Home:   https://github.com/conformal/btcutil
  Commit: 5509c323a496967b00a71a99f75af2cb03222d5b
      
https://github.com/conformal/btcutil/commit/5509c323a496967b00a71a99f75af2cb03222d5b
  Author: Dave Collins <da...@conformal.com>
  Date:   2014-12-20 (Sat, 20 Dec 2014)

  Changed paths:
    M .travis.yml
    M README.md

  Log Message:
  -----------
  Add test coverage badge to README.md.