Naming version as upcoming one with "-pre" suffix.

This is how semver marks pre-release versions.

@mkroehnert It is probably good idea to always have "-pre"
and do the release process script with that in mind
(just remove "-pre", publish, increment and add "-pre").

IIRC this is how node does it; other projects probably, too.

@NicolasPetton Maybe there are more places where version is denoted, there it also should be changed.
node engines includes 0.10 as well
taking git hash away, it should not point to exact tag

... when the version is "-pre". When released, the hash
should be added (ping @mkroehnert).
Merge pull request #623 from herby/metadata-fixes

Metadata fixes