Not sure what you mean by gemmed out.
I believe that you should either require it in application.js (in
which case it will be compiled in with the other js files) or
specifically include it in the page using the script tag. The former
is generally preferred as it means the browser should only load the js
once for the whole website. I have not used this particular library
though so don't know whether there is a reason why it should be
explicitly loaded in the page.
Google found this which may be helpful
http://stackoverflow.com/questions/21519040/rails-4-bootstrap-set-up-assets
Colin