Bump nokogiri from 1.10.8 to 1.13.4

Bumps [nokogiri](https://github.com/sparklemotion/nokogiri) from 1.10.8 to 1.13.4.
- [Release notes](https://github.com/sparklemotion/nokogiri/releases)
- [Changelog](https://github.com/sparklemotion/nokogiri/blob/v1.13.4/CHANGELOG.md)
- [Commits](sparklemotion/nokogiri@v1.10.8...v1.13.4)

---
updated-dependencies:
- dependency-name: nokogiri
  dependency-type: indirect
...

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

Author: dependabot[bot]

Gemfile.lock

@@ -110,21 +110,23 @@ GEM
     mime-types (3.2.2)
       mime-types-data (~> 3.2015)
     mime-types-data (3.2018.0812)
-    mini_portile2 (2.4.0)
+    mini_portile2 (2.8.0)
     minitest (5.11.3)
     multi_json (1.13.1)
     net-sftp (2.1.2)
       net-ssh (>= 2.6.5)
     net-ssh (5.0.2)
-    nokogiri (1.10.8)
-      mini_portile2 (~> 2.4.0)
+    nokogiri (1.13.4)
+      mini_portile2 (~> 2.8.0)
+      racc (~> 1.4)
     padrino-helpers (0.12.9)
       i18n (~> 0.6, >= 0.6.7)
       padrino-support (= 0.12.9)
       tilt (>= 1.4.1, < 3)
     padrino-support (0.12.9)
       activesupport (>= 3.1)
     ptools (1.3.5)
+    racc (1.6.0)
     rack (1.6.12)
     rack-livereload (0.3.17)
       rack