Fix others additional lints

app/models/ability.rb

@@ -1,7 +1,7 @@
 class Ability
   include CanCan::Ability
 
-  def initialize(user)
+  def initialize(user) # rubocop:disable Lint/UnusedMethodArgument
     # Define abilities for the passed in user here. For example:
     #
     #   user ||= User.new # guest user (not logged in)

app/models/conference.rb

@@ -639,7 +639,7 @@ class Conference < ActiveRecord::Base
   # ====Returns
   # * +Fixnum+ -> Progress in Percent
   def calculate_setup_progress(result)
-    (result.select { |k, v| v }.length / result.length.to_f * 100).round(0).to_s
+    (result.select { |_k, v| v }.length / result.length.to_f * 100).round(0).to_s
   end
 
   ##

app/models/datatable.rb

@@ -9,7 +9,7 @@ class Datatable
     @view = view
   end
 
-  def as_json(options = {})
+  def as_json
     {
         sEcho: params[:sEcho].to_i,
         iTotalRecords: @klass.count,
@@ -55,10 +55,10 @@ class Datatable
     search_for = params[:sSearch].split(' ')
     terms = {}
     which_one = -1
-    criteria = search_for.inject([]) do |criteria,atom|
+    criteria = search_for.inject([]) do |mem, atom|
       which_one += 1
       terms["search#{which_one}".to_sym] = "%#{atom}%"
-      criteria << "(#{search_cols.map{|col| "#{col} like :search#{which_one}"}.join(' or ')})"
+      mem << "(#{search_cols.map{|col| "#{col} like :search#{which_one}"}.join(' or ')})"
     end.join(' and ')
     [criteria, terms]
   end