Added changelog for version 3.5.1.

Author: jlesage

baseimagedefs.xml

@@ -130,6 +130,12 @@ container.
     </documentation>
     <!-- Changelog. -->
     <history>
+      <release>
+        <version>3.5.1</version>
+        <date>2018-09-18</date>
+        <change>Now using version 2.4.1 of `jlesage/baseimage`, which bring the following changes:</change>
+        <change level="2">Updated installed packages to get latest security fixes.</change>
+      </release>
       <release>
         <version>3.5.0</version>
         <date>2018-08-14</date>