If there's already jQuery on the page, it'll be included another time.
I think it shouldn't include jquery but rely on the developer to include it in application.js.
SHA 2323d6eeac26bd50b3d8bafe8b1f61674c29fb75 removed this automatic inclusion, and is now in 1.0.0
This is good because I can use jquery from external CDN.
If there's already jQuery on the page, it'll be included another time. I think it shouldn't include jquery but rely on the developer to include it in application.js.