It's important to think about your performance needs before you add any kind of third-party dependency. In production, you might consider using IcoMoon to create your own font with just the icons you need. [1] This library provides everything you need to do that.
The predefined classes give you flexibility when you're developing, but there's nothing stopping you from using your own names. There's also @extend in SASS that allows you to mix in icon styles to your application's classes without adding duplicate rules. [2]
[2] http://sass-lang.com/documentation/file.SASS_REFERENCE.html#...