Add Hint for checking master version (#3439)

* Add Hint for checking master version

* Update ISSUE_TEMPLATE.md

* Update ISSUE_TEMPLATE.md

.github/ISSUE_TEMPLATE.md

@@ -2,9 +2,13 @@
 Feature requests,  questions and general feedback is now handled at http://discourse.jabref.org 
 Thanks! --> 
 
+- [ ] I have tested the latest master version from http://builds.jabref.org/master/ and the problem persists
+
+
 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. -->
 
+
 Steps to reproduce:
 
 1. ...