Avoid Rack 1.6.7 in specs for now
Avoid Rack 1.6.7 in specs for now

See https://github.com/rack/rack/issues/1168
The above issue broke rack on 1.9.3

dilumnavanjana/bundler,mvz/bundler,mvz/bundler,dilumnavanjana/bundler,bundler/bundler,bundler/bundler