Fix load error in Ruby 2.5.0
Fix load error in Ruby 2.5.0

Prevents errors like the following from being returned:

    bundler: failed to load command: rake (/home/travis/.rvm/rubies/ruby-2.5.0/bin/rake)
    LoadError: cannot load such file -- bundler/dep_proxy

davy/benchmark-bigo,davy/benchmark-bigo