Emphasize that users should try out the newest version before reporti…

…ng a bug

.github/ISSUE_TEMPLATE/bug_report.md

@@ -11,7 +11,15 @@ Thanks!
 --> 
 
 JabRef version <!-- version as shown in the about box --> on <!-- Windows 10|Ubuntu 14.04|Mac OS X 10.8|... -->
-<!-- Hint: If you use a development version (available at http://builds.jabref.org/master/), ensure that you use the latest one. -->
+
+<!-- IMPORTANT NOTE ->
+<!-- 
+      Please always test if the bug is still reproducible in the latest development version.
+      We are constantly improving JabRef and some bugs may already be fixed.
+      You can download the development version at: http://builds.jabref.org/master/
+      Please make a backup of your library before you try out this version.
+      If you already use a development version, ensure that you use the latest one.
+ -->
 - [ ] I have tested the latest development version from http://builds.jabref.org/master/ and the problem persists
 
 <!-- Add a clear and concise description of what the bug is. -->