Remove one apostrophe in and reformat ISSUE_TEMPLATE

ISSUE_TEMPLATE.md

@@ -1,11 +1,19 @@
-If your issue is a bug report, replace this paragraph with a description of the problem, being sure to include at least:
+If your issue is a bug report, replace this paragraph with a description
+of the problem, being sure to include at least:
+
  - what happened,
  - what you expected to happen instead, and
  - any steps to reproduce the problem.
-Also fill out the version information below and add log output or screenshots as appropriate.
 
-If your issue is a feature request, simply replace this template text in it's entirety.
+Also fill out the version information below and add log output or
+screenshots as appropriate.
+
+If your issue is a feature request, simply replace this template text in
+its entirety.
 
 ### Version Information
+
 Syncthing Version: v0.x.y
 OS Version: Windows 7 / Ubuntu 14.04 / ...
+Browser Version: (if applicable, for GUI issues)
+