Explicitly document that kv uses regex character classes.

It was unclear that one would need to escape special regex characters
and how to do it properly.
Merge pull request #504 from relateiq/master

Explicitly document that kv uses regex character classes
- add technology principle
Detect ruby engine
- Add support for the -f flag
- update default message to be friendly with event v1
Fix variable name
- fix edge case exit status
- add more help text
Add an older support-originating test I forgot to commit
Merge branch 'master' into codec-hacking