Use tip YouCompleteMe from ycm-core org

Update to latest, community maintained, YouCompleteMe version and use
the same version on all platforms.

vimrc

@@ -38,14 +38,7 @@ Pack 'mkitt/tabline.vim'
 " YouCompleteMe
 " TODO: Try out neovim completion plugins to see if they are better
 if !platform#is_windows()
-  if platform#is_linux()
-    " YouCompleteMe with parameter completion
-    let s:YouCompleteMe = 'oblitum/YouCompleteMe'
-  else
-    " YouCompleteMe upstream works best on macOS
-    let s:YouCompleteMe = 'Valloric/YouCompleteMe'
-  endif
-  Pack s:YouCompleteMe,
+  Pack 'ycm-core/YouCompleteMe',
     \ {'type': 'opt', 'do': '!./install.py --clang-completer'}
   let g:ycm_key_list_select_completion = ['<C-n>', '<Down>']
   let g:ycm_key_list_previous_completion = ['<C-p>', '<Up>']