Add more git options + hub support

 - added a `--help` cli arg for printing usage
 - made `init-repo.js` more configurable for git workflows
 - allow creating a repo using `hub` instead of `lib/create-repo.js`
 - add a `--no-create` option to only do `init-repo.js` and not creating github remote
 - refactored test runner to be `node`  + `tap-spec` instead of `tap`. I can change that to `tap-dot` instead if wanted.

This solves https://github.com/thlorenz/gitify/issues/1

I want to get the git `init-repo.js` flow double checked by a coworker before this is ready for merge.