drop thin, it is no longer supported

Gemfile

@@ -105,7 +105,6 @@ gem 'sidekiq-statistic'
 gem 'sinatra', require: false
 gem 'execjs', require: false
 gem 'mini_racer'
-gem 'thin', require: false
 gem 'highline', require: false
 gem 'rack-protection' # security
 

Gemfile.lock

@@ -71,7 +71,6 @@ GEM
     concurrent-ruby (1.0.2)
     connection_pool (2.2.0)
     crass (1.0.2)
-    daemons (1.2.4)
     debug_inspector (0.0.2)
     diff-lcs (1.2.5)
     discourse-qunit-rails (0.0.9)
@@ -94,7 +93,6 @@ GEM
       railties (>= 3.1)
     ember-source (2.10.0)
     erubis (2.7.0)
-    eventmachine (1.2.0.1)
     excon (0.53.0)
     execjs (2.7.0)
     exifr (1.2.4)
@@ -361,10 +359,6 @@ GEM
       activesupport (>= 4.0)
       sprockets (>= 3.0.0)
     stackprof (0.2.10)
-    thin (1.7.0)
-      daemons (~> 1.0, >= 1.0.9)
-      eventmachine (~> 1.0, >= 1.0.4)
-      rack (>= 1, < 3)
     thor (0.19.1)
     thread_safe (0.3.5)
     tilt (2.0.5)
@@ -476,7 +470,6 @@ DEPENDENCIES
   sinatra
   spork-rails
   stackprof
-  thin
   timecop
   uglifier
   unf