Remove sidekiq-statistic gem.

* We don't really use it and there is an on-going issue
  with the gem not expiring keys in a Redis list which
  hasn't been fully resolved.

  https://github.com/davydovanton/sidekiq-statistic/issues/73

Gemfile

@@ -99,7 +99,6 @@ gem 'rest-client'
 gem 'rinku'
 gem 'sanitize'
 gem 'sidekiq'
-gem 'sidekiq-statistic'
 
 # for sidekiq web
 gem 'sinatra', require: false

Gemfile.lock

@@ -346,8 +346,6 @@ GEM
       connection_pool (~> 2.2, >= 2.2.0)
       rack-protection (>= 1.5.0)
       redis (~> 3.2, >= 3.2.1)
-    sidekiq-statistic (1.2.0)
-      sidekiq (>= 3.3.4, < 5)
     simple-rss (1.3.1)
     sinatra (1.4.6)
       rack (~> 1.4)
@@ -477,7 +475,6 @@ DEPENDENCIES
   seed-fu (~> 2.3.5)
   shoulda
   sidekiq
-  sidekiq-statistic
   simple-rss
   sinatra
   spork-rails

app/jobs/onceoff/clean_up_sidekiq_statistic.rb

@@ -0,0 +1,7 @@
+module Jobs
+  class GrantEmoji < Jobs::Onceoff
+    def execute_onceoff(args)
+      $redis.without_namespace.del('sidekiq:sidekiq:statistic')
+    end
+  end
+end