issue template: discourage use of hastebin
**What is the current result?**
<!-- Please provide a *full* server log, either by uploading it to this
- issue, or to a site like https://gist.github.com/ -->
+ issue, or to a site like https://gist.github.com/
+ Please avoid using hastebin, as anything uploaded there may expire
+ before we have a chance to review your log. -->
