Including many assets slows page loads down, because the browser has to make a request across the wire for each one. That's why the asset pipeline uses the manifest file to concatenate all of the assets into one giant file. One giant file is faster to load than many little files.

All this to say: You shouldn't include this here. You should include it in the manifest (application.css.sass) the same way that the other stylesheets are included.

Also, I doubt "bootstrap_buttons" is really the best name for this anymore, but it's your call.