This solves deprecated message below:
$ bundle install
or
$ bundle exec rake spec:all
The source :rubygems is deprecated because HTTP requests are insecure.
Please change your source to 'https://rubygems.org' if possible, or
'http://rubygems.org' if not.
We should take advantage of bundler. Use gemspec in the Gemfile to merge the Gemfile with the dependencies in the .gemspec file.
This solution requires rcov to be removed from .gemspec because RCov only works in MRI 1.8 and there's no way to specify platforms in the .gemspec.