Improve Docker installation (#152)

Gemfile.lock

@@ -183,7 +183,7 @@ GEM
       method_source
       rake (>= 0.8.7)
       thor (>= 0.20.3, < 2.0)
-    rake (13.0.6)
+    rake (12.3.3)
     rb-fsevent (0.11.1)
     rb-inotify (0.10.1)
       ffi (~> 1.0)
@@ -217,17 +217,6 @@ GEM
     rspec-support (3.8.3)
     ruby_dep (1.5.0)
     rubyzip (2.3.2)
-    sass (3.7.4)
-      sass-listen (~> 4.0.0)
-    sass-listen (4.0.0)
-      rb-fsevent (~> 0.9, >= 0.9.4)
-      rb-inotify (~> 0.9, >= 0.9.7)
-    sass-rails (5.1.0)
-      railties (>= 5.2.0)
-      sass (~> 3.1)
-      sprockets (>= 2.8, < 4.0)
-      sprockets-rails (>= 2.0, < 4.0)
-      tilt (>= 1.1, < 3)
     selenium-webdriver (4.1.0)
       childprocess (>= 0.5, < 5.0)
       rexml (~> 3.2, >= 3.2.5)
@@ -277,27 +266,27 @@ PLATFORMS
   ruby
 
 DEPENDENCIES
-  bootsnap (>= 1.4.2)
+  bootsnap (= 1.12.0)
   byebug
   capybara (>= 2.15)
   devise (= 4.7.3)
   factory_bot_rails (~> 5.0.2)
   httparty (= 0.18.0)
-  i18n-js
-  jbuilder (~> 2.7)
-  kaminari (~> 1.2.1)
+  i18n-js (= 3.9.2)
+  jbuilder (= 2.11.5)
+  kaminari (= 1.2.2)
   listen (>= 3.0.5, < 3.2)
-  pg (>= 0.18, < 2.0)
-  puma (~> 4.3)
+  pg (= 1.3.5)
+  puma (= 4.3.12)
   pundit (= 2.2.0)
   rails (= 6.0.5)
-  react-rails (~> 2.6.0)
+  rake (= 12.3.3)
+  react-rails (= 2.6.2)
   rspec-rails (~> 3.8.2)
-  sass-rails (~> 5)
   selenium-webdriver
   spring
   spring-watcher-listen (~> 2.0.0)
-  turbolinks (~> 5)
+  turbolinks (= 5.2.1)
   tzinfo-data
   web-console (>= 3.3.0)
   webdrivers
@@ -307,4 +296,4 @@ RUBY VERSION
    ruby 2.6.6p146
 
 BUNDLED WITH
-   1.17.2
+   2.3.0