minitest missing from development dependencies

[kplimack]

Issue Summary

Minitest is required for running the tests, but it is missing from the gemspec which defines the dependencies for the peoject.

Steps to Reproduce

bundle exec rake test

bundle exec rake test                                                                                                                                             (operations@staging_mdw1/operations)
/Users/jplimack/repos/ruby-http-client/test/test_ruby_http_client.rb:3:in `require': cannot load such file -- minitest/autorun (LoadError)
	from /Users/jplimack/repos/ruby-http-client/test/test_ruby_http_client.rb:3:in `<top (required)>'
	from /Users/jplimack/repos/ruby-http-client/vendor/ruby/2.3.0/gems/rake-0.9.6/lib/rake/rake_test_loader.rb:10:in `require'
	from /Users/jplimack/repos/ruby-http-client/vendor/ruby/2.3.0/gems/rake-0.9.6/lib/rake/rake_test_loader.rb:10:in `block (2 levels) in <main>'
	from /Users/jplimack/repos/ruby-http-client/vendor/ruby/2.3.0/gems/rake-0.9.6/lib/rake/rake_test_loader.rb:9:in `each'
	from /Users/jplimack/repos/ruby-http-client/vendor/ruby/2.3.0/gems/rake-0.9.6/lib/rake/rake_test_loader.rb:9:in `block in <main>'
	from /Users/jplimack/repos/ruby-http-client/vendor/ruby/2.3.0/gems/rake-0.9.6/lib/rake/rake_test_loader.rb:4:in `select'
	from /Users/jplimack/repos/ruby-http-client/vendor/ruby/2.3.0/gems/rake-0.9.6/lib/rake/rake_test_loader.rb:4:in `<main>'
rake aborted!
Command failed with status (1): [ruby -I"lib:test" -I"/Users/jplimack/repos/ruby-http-client/vendor/ruby/2.3.0/gems/rake-0.9.6/lib" "/Users/jplimack/repos/ruby-http-client/vendor/ruby/2.3.0/gems/rake-0.9.6/lib/rake/rake_test_loader.rb" "test/test*.rb" ]

Tasks: TOP => test
(See full trace by running task with --trace)