Adapt this Font Awesome snippet for the "New Naming Conventions in 4.0"

This replaces the `.icon` class for the new `.fa` class, makes the second argument (icon name) required and optionally allow to use the outline and direction arguments.

Following the official pattern: fa-[name]-[shape]-[o]-[direction].
Merge pull request #31 from kuroisuna/patch-1

Adapt this Font Awesome snippet for the "New Naming Conventions in 4.0"