Adding tests, updating docs and readme

- added npm and git ignores
- added a few basic tests with tape
- added a badge for testling-ci (git webhook still needs to be setup)
- cleaning up readme and package.json
- added license

You just need to add a testling hook ([see testlingify](https://github.com/thlorenz/testlingify)), then run `npm version patch` and publish `1.0.1`.