Jekyll buid fails using grunt-responsive-images -

hi terminal output when run jekyll build

    configuration file: /users/makingthings/dropbox/sites/jekyll-uh/_config.yml /usr/local/cellar/ruby/2.2.2/lib/ruby/2.2.0/rubygems/core_ext/kernel_require.rb:54:in `require': cannot load such file -- jekyll-responsive_image (loaderror)     /usr/local/cellar/ruby/2.2.2/lib/ruby/2.2.0/rubygems/core_ext/kernel_require.rb:54:in `require'     /usr/local/lib/ruby/gems/2.2.0/gems/jekyll-2.5.3/lib/jekyll/plugin_manager.rb:29:in `block in require_gems'     /usr/local/lib/ruby/gems/2.2.0/gems/jekyll-2.5.3/lib/jekyll/plugin_manager.rb:26:in `each'     /usr/local/lib/ruby/gems/2.2.0/gems/jekyll-2.5.3/lib/jekyll/plugin_manager.rb:26:in `require_gems'     /usr/local/lib/ruby/gems/2.2.0/gems/jekyll-2.5.3/lib/jekyll/plugin_manager.rb:19:in `conscientious_require'     /usr/local/lib/ruby/gems/2.2.0/gems/jekyll-2.5.3/lib/jekyll/site.rb:79:in `setup'     /usr/local/lib/ruby/gems/2.2.0/gems/jekyll-2.5.3/lib/jekyll/site.rb:41:in `initialize'     /usr/local/lib/ruby/gems/2.2.0/gems/jekyll-2.5.3/lib/jekyll/commands/build.rb:29:in `new'     /usr/local/lib/ruby/gems/2.2.0/gems/jekyll-2.5.3/lib/jekyll/commands/build.rb:29:in `process'     /usr/local/lib/ruby/gems/2.2.0/gems/jekyll-2.5.3/lib/jekyll/commands/build.rb:18:in `block (2 levels) in init_with_program'     /usr/local/lib/ruby/gems/2.2.0/gems/mercenary-0.3.5/lib/mercenary/command.rb:220:in `call'     /usr/local/lib/ruby/gems/2.2.0/gems/mercenary-0.3.5/lib/mercenary/command.rb:220:in `block in execute'     /usr/local/lib/ruby/gems/2.2.0/gems/mercenary-0.3.5/lib/mercenary/command.rb:220:in `each'     /usr/local/lib/ruby/gems/2.2.0/gems/mercenary-0.3.5/lib/mercenary/command.rb:220:in `execute'     /usr/local/lib/ruby/gems/2.2.0/gems/mercenary-0.3.5/lib/mercenary/program.rb:42:in `go'     /usr/local/lib/ruby/gems/2.2.0/gems/mercenary-0.3.5/lib/mercenary.rb:19:in `program'     /usr/local/lib/ruby/gems/2.2.0/gems/jekyll-2.5.3/bin/jekyll:20:in `<top (required)>'     /usr/local/bin/jekyll:23:in `load'     /usr/local/bin/jekyll:23:in `<main>' 

possibly conflicting ruby environments?

not familiar ruby got working config this:

gems: [jekyll/responsive_image]