Add instruction how to setup and use CodeSniffer

[jmolivas]

Add a page to the book explaining how to setup use and test this tools.

Related to: hechoendrupal/drupal-console#200

[jmolivas]

We should add instructions to:

• Verify drupal code style against generated code.
• Use phpqa against project code since we already provide a phpqa.yml file with project configurations.
• Setup a .git/hooks/pre-commit to run code verification, similar to what we implemented on the .travis file https://github.com/hechoendrupal/DrupalConsole/blob/master/.travis.yml#L39-L40 for testing the generated code.