Update jekyll dependencies to fix CVE-2018-1000201

https://nvd.nist.gov/vuln/detail/CVE-2018-1000201

Signed-off-by: Fabio Utzig <utzig@apache.org>
diff --git a/docs/Gemfile.lock b/docs/Gemfile.lock
index 303b1c7..c8c8fc8 100644
--- a/docs/Gemfile.lock
+++ b/docs/Gemfile.lock
@@ -18,7 +18,7 @@
     execjs (2.7.0)
     faraday (0.13.1)
       multipart-post (>= 1.2, < 3)
-    ffi (1.9.18)
+    ffi (1.9.24)
     forwardable-extended (2.6.0)
     gemoji (3.0.0)
     github-pages (160)
@@ -37,7 +37,7 @@
       jekyll-readme-index (= 0.1.0)
       jekyll-redirect-from (= 0.12.1)
       jekyll-relative-links (= 0.4.1)
-      jekyll-sass-converter (= 1.5.0)
+      jekyll-sass-converter (= 1.5.2)
       jekyll-seo-tag (= 2.3.0)
       jekyll-sitemap (= 1.1.1)
       jekyll-swiss (= 0.4.0)
@@ -73,7 +73,7 @@
       activesupport (>= 2)
       nokogiri (>= 1.4)
     i18n (0.8.6)
-    jekyll (3.5.2)
+    jekyll (3.7.3)
       addressable (~> 2.4)
       colorator (~> 1.0)
       jekyll-sass-converter (~> 1.0)
@@ -111,7 +111,7 @@
       jekyll (~> 3.3)
     jekyll-relative-links (0.4.1)
       jekyll (~> 3.3)
-    jekyll-sass-converter (1.5.0)
+    jekyll-sass-converter (1.5.2)
       sass (~> 3.4)
     jekyll-seo-tag (2.3.0)
       jekyll (~> 3.3)
@@ -160,14 +160,14 @@
       jekyll-seo-tag (~> 2.0)
     jekyll-titles-from-headings (0.4.0)
       jekyll (~> 3.3)
-    jekyll-watch (1.5.0)
+    jekyll-watch (2.0.0)
       listen (~> 3.0, < 3.1)
     jemoji (0.8.0)
       activesupport (~> 4.0)
       gemoji (~> 3.0)
       html-pipeline (~> 2.2)
       jekyll (>= 3.0)
-    kramdown (1.13.2)
+    kramdown (1.16.2)
     liquid (4.0.0)
     listen (3.0.6)
       rb-fsevent (>= 0.9.3)
@@ -183,7 +183,7 @@
       mini_portile2 (~> 2.2.0)
     octokit (4.7.0)
       sawyer (~> 0.8.0, >= 0.5.3)
-    pathutil (0.14.0)
+    pathutil (0.16.1)
       forwardable-extended (~> 2.6)
     public_suffix (2.0.5)
     rb-fsevent (0.10.2)
@@ -191,7 +191,7 @@
       ffi (>= 0.5.0, < 2)
     rouge (1.11.1)
     safe_yaml (1.0.4)
-    sass (3.5.1)
+    sass (3.5.5)
       sass-listen (~> 4.0.0)
     sass-listen (4.0.0)
       rb-fsevent (~> 0.9, >= 0.9.4)