Remove the tests directory from the npm package
Remove the tests directory from the npm package

It's absurdly huge and made the package 72 MB rather than 500 KB. Not packaging
the tests directory seems to be stanard for major JS projects.

realm/realm-js,realm/realm-js,realm/realm-js,realm/realm-js,realm/realm-js,realm/realm-js,realm/realm-js,realm/realm-js,realm/realm-js