redmine 4.0.0 support

[tverbeke]

redmine 4.0.0 moved to rails5; the render_parent plugin used, though, uses rails3 related code, see

http://www.redmine.org/issues/30209

[bviktor]

+1 this is quite a blocker for us :(

[bviktor]

To me, simply commenting out the gem requirement in the Gemfile eliminated this error.

But I can't say for sure if it works, because I have another plugin that prevents the Redmine 4 upgrade...

[adi-david]

Removing the "gem 'render_parent', '>= 0.0.4'" from plugin's Gemfile seem to fix it for me. Thank you!