Revert "Testsuites"

Reverts ua-parser/uap-core#11

This pull requests does way too many things at the same time, some of which needs to be discussed before they're approved.

1. it fixes a typo in the README
2. it adds a README in the test repository.
3. it refactors the JS test file
4. it adds instructions for a JS linter

These require 4 different pull requests or a discussion before.