rubygems/rubygems.org — pull request #416 by wayneeseguin (2012-04-18 12:23:54+00:00)
Title: Gemfile is a better word to indicate what the following line is for.

I just pushed a new gem and was looking at the gem page.

I believe that it would be less confusing to say 'Gemfile' instead of 'Bundler' so that it indicates that the user will put that line into their 'Gemfile'.