Bundler not resolving the right dependencies

I believe that you need to specify pre and beta versions explicitly in your Gemfile.

source 'https://rubygems.org'
gemspec

gem 'minitest-ci'

group :development do
  gem 'git-precommit'
  gem 'steep', '0.1.0.pre'
  gem 'yard'
end

With that said, that version is set to >= 0 for Ruby compatibility and the next one 0.1.0.pre2 was set for >= 2.4.0. So there is a possibility ‘steep’ is not actually compatible with Ruby 2.2.2, but the original authors did not set the compatibility on that first version. Still might be worth a shot though.