Update gems.

Gemfile

@@ -7,7 +7,7 @@ gem "rake", require: false
 gem "irb"
 gem "rack"
 gem "sinatra"
-gem "puma"
+gem "puma", "~> 4.3"
 gem "dotenv"
 gem "redis"
 gem "redis-namespace"

Gemfile.lock

@@ -14,7 +14,6 @@ GEM
       airbrake-ruby (~> 5.0)
     airbrake-ruby (5.0.2)
       rbtree3 (~> 0.5)
-    backports (3.18.2)
     coderay (1.1.3)
     concurrent-ruby (1.1.7)
     crass (1.0.6)
@@ -26,8 +25,8 @@ GEM
       rake (>= 12)
     heroku-env (0.1.4)
     io-console (0.5.6)
-    irb (1.2.4)
-      reline (>= 0.0.1)
+    irb (1.2.6)
+      reline (>= 0.1.5)
     loofah (2.7.0)
       crass (~> 1.0.2)
       nokogiri (>= 1.5.9)
@@ -36,8 +35,8 @@ GEM
     multi_json (1.15.0)
     mustermann (1.1.1)
       ruby2_keywords (~> 0.0.1)
-    newrelic_rpm (6.12.0.367)
-    nio4r (2.5.2)
+    newrelic_rpm (6.13.0)
+    nio4r (2.5.4)
     nokogiri (1.10.10)
       mini_portile2 (~> 2.4.0)
     opengraph_parser (0.2.3)
@@ -51,34 +50,33 @@ GEM
     pry-remote (0.1.8)
       pry (~> 0.9)
       slop (~> 3.0)
-    public_suffix (4.0.5)
-    puma (4.3.5)
+    public_suffix (4.0.6)
+    puma (4.3.6)
       nio4r (~> 2.0)
     rack (2.2.3)
-    rack-protection (2.0.8.1)
+    rack-protection (2.1.0)
       rack
     rack-ssl-enforcer (0.2.9)
     rake (13.0.1)
     rbtree3 (0.6.0)
-    redis (4.2.1)
+    redis (4.2.2)
     redis-namespace (1.8.0)
       redis (>= 3.0.4)
-    reline (0.1.4)
+    reline (0.1.5)
       io-console (~> 0.5)
     ruby2_keywords (0.0.2)
     sax-machine (1.3.2)
     secure_headers (6.3.1)
-    sinatra (2.0.8.1)
+    sinatra (2.1.0)
       mustermann (~> 1.0)
-      rack (~> 2.0)
-      rack-protection (= 2.0.8.1)
+      rack (~> 2.2)
+      rack-protection (= 2.1.0)
       tilt (~> 2.0)
-    sinatra-contrib (2.0.8.1)
-      backports (>= 2.8.2)
+    sinatra-contrib (2.1.0)
       multi_json
       mustermann (~> 1.0)
-      rack-protection (= 2.0.8.1)
-      sinatra (= 2.0.8.1)
+      rack-protection (= 2.1.0)
+      sinatra (= 2.1.0)
       tilt (~> 2.0)
     slop (3.6.0)
     thor (1.0.1)
@@ -104,7 +102,7 @@ DEPENDENCIES
   powder
   prometheus-client!
   pry-remote
-  puma
+  puma (~> 4.3)
   rack
   rack-ssl-enforcer
   rake