chore(security): patch nokogiri vulnerability (#346)

Author: dependabot[bot]

Gemfile.lock

@@ -84,11 +84,11 @@ GEM
     mail (2.7.0)
       mini_mime (>= 0.1.1)
     mini_mime (1.0.0)
-    mini_portile2 (2.3.0)
+    mini_portile2 (2.4.0)
     minitest (5.11.3)
     multi_xml (0.6.0)
-    nokogiri (1.8.1)
-      mini_portile2 (~> 2.3.0)
+    nokogiri (1.10.8)
+      mini_portile2 (~> 2.4.0)
     rack (1.6.10)
     rack-cors (0.4.0)
     rack-test (0.6.3)