Add note about using render without a partial path
Add note about using render without a partial path

When the collection is empty, the partial path is `nil`
(https://github.com/rails/rails/blob/master/actionview/lib/action_view/renderer/partial_renderer.rb#L384..L385),
and the renderer cannot find a template that can be monkey-patched
(https://github.com/rails/rails/blob/master/actionview/lib/action_view/renderer/partial_renderer.rb#L418).

This is expected behaviour from ActionView, so I think we should just
update the README to make it clear.

Related to #8, #11.

[ci skip]

amatsuda/jb,amatsuda/jb,amatsuda/jb,amatsuda/jb