switched back from webrick to thin

I avoided Thin before to not add an eventmachine dependency, but we're now using eventmachine anyway

Gemfile

···
 gem 'rainbow'
 
 group :development do
-  gem 'webrick'
+  gem 'thin'
   gem 'capistrano', '~> 2.0'
 end

Gemfile.lock

···
       net-ssh-gateway (>= 1.1.0)
     cbor (0.5.9.6)
     concurrent-ruby (1.2.2)
+    daemons (1.4.1)
     eventmachine (1.2.7)
     faye-websocket (0.11.3)
       eventmachine (>= 0.12.0)
···
       faye-websocket (~> 0.11.2)
     sqlite3 (1.6.7-arm64-darwin)
     sqlite3 (1.6.7-x86_64-linux)
+    thin (1.8.2)
+      daemons (~> 1.0, >= 1.0.9)
+      eventmachine (~> 1.0, >= 1.0.4)
+      rack (>= 1, < 3)
     tilt (2.3.0)
     tzinfo (2.0.6)
       concurrent-ruby (~> 1.0)
-    webrick (1.8.1)
     websocket-driver (0.7.6)
       websocket-extensions (>= 0.1.0)
     websocket-extensions (0.1.5)
···
   sinatra-activerecord (~> 2.0)
   skyfall (~> 0.2, >= 0.2.3)
   sqlite3
-  webrick
+  thin
 
 BUNDLED WITH
    2.4.19