As documented in this discussion from July 2010, requiring ./config/boot in Capistrano's deploy.rb effectively breaks the deployment ("could not find any strategy named `[any strategy]'").
Removing the line require './config/boot' from deploy.rb makes everything work again.
I am wondering why this is still in the generator? Would you accept a pull request that removes the line?
I ran into the same problem when adding Airbrake to my application. It turned out that removing require './config/boot' line fixed this problem for me as well.