Correct version string for --version flag (master)

[MPLew-is]

This is going to be a pain to keep bumping for every release, but this change at least gets the correct version in for now.

Feel free to close this or #201 if you don't feel both are necessary, but since it seems like you'd cherry pick this commit anyway between the branches, I figured I'd save you some time and make them separate PRs.

[allevato]

Thank you for taking a look at this.

Long-term, I think it would be ideal if Swift Package Manager had some way to automatically generate and inject version info for projects—I've been meaning to start a conversation about this on the forums but haven't had the time to really foster that discussion, but maybe I should just kick something off and see where it goes.

In the meantime, it'll be good to have these strings actually reflect reality since we've cut a couple releases already.

[MPLew-is]

I wholeheartedly agree it would be useful to have some way of accessing some versioning information from Swift Package Manager, but I'm not sure what easy mechanism there would be for embedding that information into the end binary. Would love to see a discussion on the subject though.