Merge pull request #872 from puremourning/dependabot/bundler/docs/rexml-3.3.3

Bump rexml from 3.2.8 to 3.3.3 in /docs

Author: puremourning

docs/Gemfile.lock

@@ -224,8 +224,8 @@ GEM
     rb-fsevent (0.11.2)
     rb-inotify (0.10.1)
       ffi (~> 1.0)
-    rexml (3.2.8)
-      strscan (>= 3.0.9)
+    rexml (3.3.3)
+      strscan
     rouge (3.26.0)
     ruby2_keywords (0.0.5)
     rubyzip (2.3.2)