remove hard-coded assets path for ace editor modules

app/assets/javascripts/lib/ace.js

-/*= require ace-rails-ap */
+/*= require ace/ace */
 /*= require ace/ext-searchbox */
+/*= require ./ace/ace_config_paths */

app/assets/javascripts/lib/ace/ace_config_paths.js.erb

+<%
+ace_gem_path = Bundler.rubygems.find_name('ace-rails-ap').first.full_gem_path
+ace_workers = Dir[ace_gem_path + '/vendor/assets/javascripts/ace/worker-*.js'].sort.map do |file|
+  File.basename(file, '.js').sub(/^worker-/, '')
+end
+ace_modes = Dir[ace_gem_path + '/vendor/assets/javascripts/ace/mode-*.js'].sort.map do |file|
+  File.basename(file, '.js').sub(/^mode-/, '')
+end
+%>
+
+(function() {
+  window.gon = window.gon || {};
+  var basePath = (window.gon.relative_url_root || '').replace(/\/$/, '') + '/assets/ace';
+  ace.config.set('basePath', basePath);
+
+  // configure paths for all worker modules
+<% ace_workers.each do |worker| %>
+  ace.config.setModuleUrl('ace/mode/<%= worker %>_worker', basePath + '/worker-<%= worker %>.js');
+<% end %>
+
+  // configure paths for all mode modules
+<% ace_modes.each do |mode| %>
+  ace.config.setModuleUrl('ace/mode/<%= mode %>', basePath + '/mode-<%= mode %>.js');
+<% end %>
+})();