Update dependencies

Gemfile.lock

@@ -16,7 +16,7 @@ GEM
     coffee-script-source (1.12.2)
     colorator (1.1.0)
     commonmarker (0.23.10)
-    concurrent-ruby (1.3.3)
+    concurrent-ruby (1.3.4)
     dnsruby (1.72.2)
       simpleidn (~> 0.2.1)
     em-websocket (0.5.3)
@@ -213,7 +213,7 @@ GEM
       jekyll (>= 3.5, < 5.0)
       jekyll-feed (~> 0.9)
       jekyll-seo-tag (~> 2.1)
-    minitest (5.24.1)
+    minitest (5.25.1)
     nokogiri (1.13.10)
       mini_portile2 (~> 2.8.0)
       racc (~> 1.4)
@@ -227,7 +227,7 @@ GEM
     rb-fsevent (0.11.2)
     rb-inotify (0.11.1)
       ffi (~> 1.0)
-    rexml (3.3.4)
+    rexml (3.3.6)
       strscan
     rouge (3.30.0)
     ruby2_keywords (0.0.5)