* Add depend on the `vergen` crate (only use the `build` and `git`
features)
* Add the build script `build.rs` to setup the environment variables
from the build system
* Update the printed version information to use these environment
variables
* Introduce an error JSON output
* Return error JSON output if the status data is not there (yet)
* Introduce a default catcher to return error JSON output in all other
unsupported/unhandled cases
* Update the documentation
Paul van Tilburg