Update outdated dependencies

Two rexml releases with security fixes

Author: javierjulio

Gemfile.lock

@@ -118,7 +118,7 @@ GEM
       railties (>= 4.1.0)
       responders
       warden (~> 1.2.3)
-    docile (1.4.0)
+    docile (1.4.1)
     drb (2.2.1)
     erubi (1.13.0)
     formtastic (5.0.0)
@@ -245,7 +245,7 @@ GEM
     responders (3.1.1)
       actionpack (>= 5.2)
       railties (>= 5.2)
-    rexml (3.3.2)
+    rexml (3.3.4)
       strscan
     ruby2_keywords (0.0.5)
     rubyzip (2.3.2)