Linux version awareness

[cespare]

Right now there's Lucid-specific stuff in Terraform. We should figure out what we're running on and then have a mechanism for doing different things depending on what Ubuntu it is. We should also fail if we don't now how to handle the version we're running on.

[philc]

What specifically is lucid dependent?

[cespare]

The 'git-core' package is just called 'git' in later Ubuntu versions.

There's also no guarantee that the other package names ("curl", "build-essential", "libxslt1-dev", "libxml2-dev", "libssl-dev") will remain valid in future releases.

[cespare]

For now, I'm just going to change git-core to git, I think. Even if you're on Lucid, you could get around this by installing the git ppa or just using an older Terraform version.

[cespare]

I pushed a prerelease version of the gem (0.0.7.rc1) with this change. @philc let me know what you think.