Error when trying to run tests as described in README

[SKoschnicke]

The README.md states:

To run the test suite locally against all supported frameworks:

% bundle install
% rake spec:all

But this results in

> rake spec:all
BUNDLE_GEMFILE='gemfiles/rails-3-2-stable.gemfile' bundle -j 4 --quiet
Could not find gem 'rake (< 11.0)' in any of the gem sources listed in your Gemfile.
Run `bundle install` to install missing gems.
rake aborted!
Command failed with status (7): [BUNDLE_GEMFILE='gemfiles/rails-3-2-stable....]
/home/svk/development/sc/simple-navigation/Rakefile:23:in `block (3 levels) in <top (required)>'
/home/svk/.rbenv/versions/2.4.1/bin/bundle:22:in `load'
/home/svk/.rbenv/versions/2.4.1/bin/bundle:22:in `<main>'
Tasks: TOP => spec:all => spec:rails-3-2-stable
(See full trace by running task with --trace)

Only when running bundle install with BUNDLE_GEMFILE='gemfiles/rails-3-2-stable.gemfile', rake spec:all works.