Now that libcni has the ability to print a version message, plumb it
through correctly.
While we're at it,
- fix import paths
- run gofmt
- add some more comments to sample
- add container runtime swappability for release
In real-world address allocations, disjoint address ranges are common.
Therefore, the host-local allocator should support them.
This change still allows for multiple IPs in a single configuration, but
also allows for a "set of subnets."
Fixes: #45
