Don't know if it's a Ruby 2 / OSX Mavericks issue, but the setup fails with
git reflow setup
/Users/ea/.rbenv/versions/2.0.0-p247/lib/ruby/2.0.0/rubygems/core_ext/kernel_require.rb:45:in `require': cannot load such file -- json/pure (LoadError)
from /Users/ea/.rbenv/versions/2.0.0-p247/lib/ruby/2.0.0/rubygems/core_ext/kernel_require.rb:45:in `require'
from /Users/ea/.rbenv/versions/2.0.0-p247/lib/ruby/gems/2.0.0/gems/git_reflow-0.3.3/lib/git_reflow.rb:6:in `<top (required)>'
from /Users/ea/.rbenv/versions/2.0.0-p247/lib/ruby/2.0.0/rubygems/core_ext/kernel_require.rb:45:in `require'
from /Users/ea/.rbenv/versions/2.0.0-p247/lib/ruby/2.0.0/rubygems/core_ext/kernel_require.rb:45:in `require'
from /Users/ea/.rbenv/versions/2.0.0-p247/lib/ruby/gems/2.0.0/gems/git_reflow-0.3.3/bin/git-reflow:16:in `<top (required)>'
from /Users/ea/.rbenv/versions/2.0.0-p247/bin/git-reflow:23:in `load'
from /Users/ea/.rbenv/versions/2.0.0-p247/bin/git-reflow:23:in `<main>'
Don't know if it's a Ruby 2 / OSX Mavericks issue, but the setup fails with