avoid parsing argv when using as a lib #8
Description
when requiring this lib for use in an external codebase the lib/oa.js file calls minimist from the module scope to process process.argv.
this in turn leads to requiring minimist as a runtime dep when not using the CLI interface.
https://github.com/openaddresses/lib/blob/master/oa.js#L11-L18
one potential solution is to use something like this if (require.main === module) { to distinguish between execution and inclusion.
alternatively this functionality could be moved to lib/src/cli.js and only run when the CLI interface is executed.