favor unless over if with a single negative condition
Merge pull request #274 from hasghari/conditional

favor unless with positive condition over if with negative condition
Add single-quotes to indent example
Merge pull request #276 from thiagogabriel/fix/single-quote-example

Add single-quotes to indent example
naming files
recommendation to have single class/module per file
Merge pull request #277 from deric/master

naming files
Merge remote ‘bbatsov/master’