Don't report WIP versions as releases.
Add flag to enable/disable SSL cert check.
We disabled SSL certificate checks for wget and curl a while ago,
when we first added https repositories. We'll keep the check disabled
by default for now, but this adds a config option,
`check_certificates=true` that can be used in your config.lua.
Merge branch 'master' of https://github.com/keplerproject/luarocks