[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)

Oh sorry forgot about it. I thought the comment block was duplicated but it looks like as this is by intention. File doc and class doc. I've not checked the code styleguides before.