Use bundler < 2 on travis
Use bundler < 2 on travis

Travis says:

    Bundler could not find compatible versions for gem "bundler"
      In Gemfile:
        bundler (~> 1.5)
      Current Bundler version:
        bundler (2.0.1)

Found the solution at https://docs.travis-ci.com/user/languages/ruby/#bundler-20

I guess we could also change the version we use in our gemspec file,
but since we don't use v2 anywhere else I solved it like this instead.

twingly/capistrano-twingly