version number

[xlc]

          best to not hardcode the version number here

in other projects this is what we do:

• read version from compile time defined variable, and fallback to short git commit ref
• when making releases, have the release script to supply the proper version

not sure if spm supports build script to get git commit ref but we can totally have a defined variable and fallback to dev if we can't get git commit ref

Originally posted by @xlc in #165 (comment)