[FEATURE] Add a colored diff report

```phpcs --standard=Generic --extensions=php --report=coloreddiff --sniffs=Generic.WhiteSpace.DisallowSpaceIndent -vs CodeSniffer/Standards/Generic/Tests/WhiteSpace/DisallowSpaceIndentUnitTest.inc```

![coloreddiffoutput](https://cloud.githubusercontent.com/assets/363363/5558734/bf7d550e-8d32-11e4-9334-d29e477292d6.png)

Don't understand. What do you mean?