update development instructions

DEVELOPING.md

 
 ## Releasing a new version
 
-1. Run [`irctest`]() over it to make sure nothing's severely broken.
+1. Test backwards compatibility guarantees. Get an example config file and an example database from the previous stable release. Make sure the current build still works with them (modulo anything explicitly called out in the changelog as a breaking change).
+1. Run `irctest` over it to make sure nothing's severely broken. Talk to the maintainers to find out which version of irctest to run.
 1. Update the changelog with new changes and write release notes.
 1. Update the version number `irc/constants.go` (either change `-unreleased` to `-rc1`, or remove `-rc1`, as appropriate).
 1. Commit the new changelog and constants change.