Update issue templates

Author: tobiasdiez

.github/ISSUE_TEMPLATE/bug_report.md

@@ -0,0 +1,32 @@
+---
+name: Bug report
+about: Create a report to help us improve
+
+---
+
+<!-- 
+Note: Please use the GitHub issue tracker only for bug reports. 
+Feature requests, questions and general feedback is now handled at http://discourse.jabref.org.
+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. -->
+- [ ] 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. -->
+
+Steps to reproduce the behavior:
+1. ...
+2. ...
+3. ...
+
+<!-- If applicable, add excerpt of the bibliography file, screenshot, and excerpt of log (available in the error console) -->
+
+<details>
+  <summary>Log File</summary>
+  
+  ```
+  Paste an excerpt of your log file here
+  ```
+</details>