[meta] Exclude tests and config files from publish

[dosisod]

Tests and config files don't need to be in the published package (the test folder alone is over half the size of the total package!). We might want to keep the example folder though, so I can change that if we want to keep it in the release.

[ljharb]

Yes, they absolutely need to be in the published package - npm explore foo && npm install && npm test should always work. Those files must be included, and will forever be.

Note that this would be a breaking change.

Duplicate of #281. Duplicate of #279. Duplicate of #239. Duplicate of #235. Duplicate of #58. Duplicate of #44. See #105 (comment).