Gemfile: replace thin with puma (for now only in dev)

Gemfile

@@ -96,7 +96,7 @@ end
 
 group :development, :test do
   gem 'rake'
-  gem 'thin'
+  gem 'puma'
   gem 'rspec-rails', '~> 3.5'
   gem 'factory_girl_rails', require: false
   gem 'faker'

Gemfile.lock

@@ -111,7 +111,6 @@ GEM
     concurrent-ruby (1.0.5)
     connection_pool (2.2.1)
     crass (1.0.4)
-    daemons (1.2.4)
     database_cleaner (1.5.3)
     debug_inspector (0.0.2)
     delayed_paperclip (3.0.1)
@@ -130,7 +129,6 @@ GEM
       unf (>= 0.0.5, < 1.0.0)
     equalizer (0.0.11)
     erubis (2.7.0)
-    eventmachine (1.2.3)
     excon (0.55.0)
     execjs (2.7.0)
     factory_girl (4.8.0)
@@ -383,6 +381,7 @@ GEM
       net-ssh (>= 2.6.5)
     net-ssh (4.1.0)
     newrelic_rpm (4.2.0.334)
+    nio4r (2.5.2)
     nokogiri (1.10.2)
       mini_portile2 (~> 2.4.0)
     nokogumbo (2.0.1)
@@ -423,6 +422,8 @@ GEM
       method_source (~> 0.8.1)
       slop (~> 3.4)
     public_suffix (2.0.5)
+    puma (4.3.3)
+      nio4r (~> 2.0)
     rack (1.6.11)
     rack-pjax (1.0.0)
       nokogiri (~> 1.5)
@@ -565,10 +566,6 @@ GEM
       net-ssh (>= 2.8.0)
     sweetalert-rails (1.1.3)
       railties (>= 3.1.0)
-    thin (1.7.0)
-      daemons (~> 1.0, >= 1.0.9)
-      eventmachine (~> 1.0, >= 1.0.4)
-      rack (>= 1, < 3)
     thor (0.19.4)
     thread_safe (0.3.6)
     tilt (1.4.1)
@@ -672,6 +669,7 @@ DEPENDENCIES
   pg
   pghero
   poltergeist
+  puma
   questiongenerator!
   rails (~> 4.2.11, >= 4.2.11.1)
   rails-assets-growl
@@ -694,7 +692,6 @@ DEPENDENCIES
   sinatra
   spring (~> 1.3.5)
   sweetalert-rails
-  thin
   tiny-color-rails
   tumblr_client
   turbolinks (~> 2.5.3)