Adds issue template fixes #841

thanks @flavioribeiro for the heads up

issue_template.md

@@ -0,0 +1,17 @@
+**Browser**: FILL WITH YOUR BROWSER (ex: Chrome Version 46.0.2490.80, Firefox Version 3.5.6, IE 11)
+
+**OS**: FILL WITH YOUR OS (ex: Mac OS 10.11.1, iOS9, android4.5)
+
+**Clappr Version**: 0.2.25
+
+**Steps to reproduce**:
+
+* first step
+* then second step
+* I was expecting X but instead it shows Y
+
+Did you try to reproduce this issue at http://cdn.clappr.io/
+
+ps: you can attach images, logs or whatever you think might be helpful.
+ps: feel free to clean this if your issue is different.
+