fix npm publish package

[mandolyte]

After reading this: yarnpkg/yarn#685

I experimented using the yarn pack command. It now produces a package that only contains 48 files/directories instead of the thousands it had before.

The changes are these:

• changes to the syntax used in .npmignore
• additions to the same (in order to fit well with .gitignore)
• removal of the "files" section in package.json

I do not know why the last one exists in the first place. So you may want to publish a beta first and what ends up in NPM.

---

This change is