Add "tap-diff" and "tap-notify" to README

Author: axross

readme.markdown

@@ -89,6 +89,8 @@ that will output something pretty if you pipe TAP into them:
  - https://github.com/aghassemi/tap-xunit
  - https://github.com/namuol/tap-difflet
  - https://github.com/gritzko/tape-dom
+ - https://github.com/axross/tap-diff
+ - https://github.com/axross/tap-notify
 
 To use them, try `node test/index.js | tap-spec` or pipe it into one
 of the modules of your choice!