Update dependency thin to ~> 1.8.1

Gemfile.lock

@@ -19,7 +19,7 @@ GEM
       execjs
     coffee-script-source (1.12.2)
     concurrent-ruby (1.1.9)
-    daemons (1.3.1)
+    daemons (1.4.0)
     erubi (1.9.0)
     ethon (0.12.0)
       ffi (>= 1.3.0)
@@ -64,7 +64,7 @@ GEM
     pry (0.14.1)
       coderay (~> 1.1)
       method_source (~> 1.0)
-    rack (2.0.7)
+    rack (2.2.3)
     rack-protection (2.0.7)
       rack
     rack-ssl-enforcer (0.2.9)
@@ -106,7 +106,7 @@ GEM
     strings-ansi (0.1.0)
     terminal-table (1.8.0)
       unicode-display_width (~> 1.1, >= 1.1.1)
-    thin (1.7.2)
+    thin (1.8.1)
       daemons (~> 1.0, >= 1.0.9)
       eventmachine (~> 1.0, >= 1.0.4)
       rack (>= 1, < 3)