Replace thin with puma.

Gemfile

@@ -21,5 +21,5 @@ group :development do
 end
 
 group :production do
-  gem 'thin'
+  gem 'puma'
 end

Gemfile.lock

@@ -7,10 +7,8 @@ GEM
       coffee-script-source
       execjs
     coffee-script-source (1.6.3)
-    daemons (1.1.9)
     diff-lcs (1.2.4)
     dotenv (0.9.0)
-    eventmachine (1.0.3)
     execjs (2.0.2)
     foreman (0.63.0)
       dotenv (>= 0.7)
@@ -22,6 +20,8 @@ GEM
       coderay (~> 1.0.5)
       method_source (~> 0.8)
       slop (~> 3.4)
+    puma (2.6.0)
+      rack (>= 1.1, < 2.0)
     rack (1.5.2)
     rack-protection (1.5.0)
       rack
@@ -70,10 +70,6 @@ GEM
     sprockets-sass (1.0.2)
       sprockets (~> 2.0)
       tilt (~> 1.1)
-    thin (1.6.0)
-      daemons (>= 1.0.9)
-      eventmachine (>= 1.0.0)
-      rack (>= 1.5.0)
     thor (0.18.1)
     tilt (1.4.1)
 
@@ -83,6 +79,7 @@ PLATFORMS
 DEPENDENCIES
   foreman
   pry
+  puma
   rspec
   rspec-mocks
   ruby-mpd
@@ -90,4 +87,3 @@ DEPENDENCIES
   sinatra
   sinatra-asset-pipeline
   sinatra-contrib
-  thin