Bump puma from 3.12.1 to 4.0.1

Bumps [puma](https://github.com/puma/puma) from 3.12.1 to 4.0.1.
- [Release notes](https://github.com/puma/puma/releases)
- [Changelog](https://github.com/puma/puma/blob/master/History.md)
- [Commits](puma/puma@v3.12.1...v4.0.1)

Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

Gemfile.lock

@@ -101,6 +101,7 @@ GEM
     mini_mime (1.0.1)
     mini_portile2 (2.4.0)
     minitest (5.11.3)
+    nio4r (2.4.0)
     nokogiri (1.10.3)
       mini_portile2 (~> 2.4.0)
     parallel (1.17.0)
@@ -110,7 +111,8 @@ GEM
       eventmachine (= 1.0.9)
       ffi
     public_suffix (3.0.3)
-    puma (3.12.1)
+    puma (4.0.1)
+      nio4r (~> 2.0)
     quiet_assets (1.1.0)
       railties (>= 3.1, < 5.0)
     rack (1.6.11)