Cleanup some of the HowDoIReportProblems

* Use lists more to make it prettier/simpler to read.
* Use 'uname -a' instead of 'uname -r' to get more relevant info.
* Request SPL/ZFS version and where it came from (show examples
  how to retrieve it).
* Include information about the 'GitHub Markup Language' (triple
  backticks for large blocks of texts).
* Include a template example for initial report.
* Remove the '> ' part from the code block that retrieves stack
  traces for processes so that it's simpler to cut-and-past.
* Request spl/zfs module parameter values for issue reports.
* Add some information about possibly upgrading to verify that the
  problem occurs in latest version.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #12