Update issue_template.md

.github/issue_template.md

@@ -1,8 +1,10 @@
 [Describe your issue]
 
+[**If you are using the `MASTER` branch, please check out the `DEV` branch before reporting any issue**]
+
 #### Check all that apply (change to `[x]`)
 - [ ] Windows
 - [ ] Mac OS X
 - [ ] Linux
 
-See <https://libigl.github.io/CONTRIBUTING/#bugreport> for more tips.
+See https://libigl.github.io/CONTRIBUTING/#bugreport for more tips.