Align versioning

[lordmauve]

The Rust binary is versioned at 0.1.0; the Debian control files for the C version as 1.0.

We should get these all aligned, and maybe add bumpversion to ensure that these are updated together?

[geofft]

I think we should imagine the Debian packaging as provisional until it gets uploaded to actual Debian, but maybe it'd be clearer if we lower the version in the packaging files for now (for the sake of people building it from source themselves).

One constraint is that our internal package is at 1.0~ts1 (in Debian versions, tilde sorts before empty-string, so this comes just before 1.0 but after any 0.x), so it's going to be smoothest if we get to 1.0 pretty quickly. But I think we should sort out the full semantics of relexec for 1.0 and ideally never have backwards-incompatible versions.