Update package.json for publishing to npm

address #2078

- removes private: true flag from package.json
- created .npmignore file to exclude files
 from being included in the npm package


So as I currently understand it, `npm publish` will take all contents in the folder (excluding those specified in the `.npmignore` file) and pack that to be included in the npm package.

This means that it'll include the compiled assets by default, addressing item 1 in #2078.  However before publishing we need to ensure `grunt prod` is run so the assets are up to date.

I previously tried doing that with the `prepublish` script ([docs here](https://www.npmjs.org/doc/misc/npm-scripts.html)) however that is also ran on `npm install`, something we cannot do.

The publish process looks like this:

```
grunt prod
npm publish
```

Which we could turn into a grunt task however that seems necessary.

That part is up to you @ErisDS, as you'll be the one doing the publishing ;).