Switched to using Puma as the app server.

Gemfile.lock

@@ -115,6 +115,8 @@ GEM
     capistrano-bundler (1.1.4)
       capistrano (~> 3.1)
       sshkit (~> 1.2)
+    capistrano-puma (0.2.3)
+      capistrano (>= 3.0)
     capistrano-rails (1.1.8)
       capistrano (~> 3.1)
       capistrano-bundler (~> 1.1)
@@ -156,7 +158,6 @@ GEM
       coffee-rails (>= 3.2.0)
       railties (>= 3.2.0)
       sass-rails (>= 3.2.0)
-    kgio (2.11.2)
     loofah (2.2.2)
       crass (~> 1.0.2)
       nokogiri (>= 1.5.9)
@@ -178,6 +179,7 @@ GEM
       mini_portile2 (~> 2.3.0)
     nokogumbo (1.5.0)
       nokogiri
+    puma (3.11.4)
     rack (1.6.9)
     rack-test (0.6.3)
       rack (>= 1.0)
@@ -194,7 +196,6 @@ GEM
       ruby-graphviz (~> 1.2)
     rails-html-sanitizer (1.0.4)
       loofah (~> 2.2, >= 2.2.2)
-    raindrops (0.19.0)
     rake (12.3.0)
     rb-fsevent (0.10.3)
     rb-inotify (0.9.10)
@@ -244,9 +245,6 @@ GEM
     unf (0.1.4)
       unf_ext
     unf_ext (0.0.7.5)
-    unicorn (5.4.0)
-      kgio (~> 2.6)
-      raindrops (~> 0.7)
     webrick (1.4.2)
 
 PLATFORMS
@@ -258,9 +256,10 @@ DEPENDENCIES
   bcrypt
   better_errors
   binding_of_caller
-  capistrano-bundler (~> 1.1.3)
-  capistrano-rails (~> 1.1.2)
-  capistrano-rbenv (~> 2.0)
+  capistrano-bundler
+  capistrano-puma
+  capistrano-rails
+  capistrano-rbenv
   highlight_js-rails!
   hirb
   jquery-rails
@@ -268,6 +267,7 @@ DEPENDENCIES
   kaminari!
   mail-gpg!
   mysql2
+  puma
   rails!
   rails-erd
   rb-readline
@@ -279,7 +279,6 @@ DEPENDENCIES
   strip_attributes
   tzinfo-data
   uglifier
-  unicorn
   webrick
 
 BUNDLED WITH