Add some extra details to .github/ISSUE_TEMPLATE.md [skip ci]

Supercedes and Fixes #1695; thanks to Anatoli Babenia.

.github/ISSUE_TEMPLATE.md

-* gevent version:
-* Python version: Please be as specific as possible: "cPython 2.7.9 downloaded from python.org"
-* Operating System: Please be as specific as possible: "Raspbian (Debian Linux 8.0 Linux 4.9.35-v7+  armv7l)"
+* gevent version: Please note how you installed it: From source, from
+                  PyPI, from your operating system's package, etc.
+* Python version: Please be as specific as possible. For example,
+                  "cPython 2.7.9 downloaded from python.org"
+* Operating System: Please be as specific as possible. For example,
+                  "Raspbian (Debian Linux 8.0 Linux 4.9.35-v7+  armv7l)"
 
 ### Description:
 
 **REPLACE ME**: What are you trying to get done, what has happened, what went wrong, and what did you expect?
 
-```
+**IMPORTANT**: Please DO NOT POST SCREENSHOTS OF TEXT. Copy and paste
+the actual text. This means: No screenshots of your editor. No
+screenshots of tracebacks or console output.
+
+```python-traceback
 Remember to put tracebacks in literal blocks
 ```
 
 ### What I've run:
 
-**REPLACE ME**: Paste short, self contained, correct example code (sscce.org), tracebacks, etc, here
+**REPLACE ME**: Paste short, self contained, correct example code (See
+http://sscce.org), tracebacks, etc, here
 
 
 ```python