Update dependencies / Fix .npmignore

* I updated dependencies and devDependencies.
  * [should#include](https://github.com/shouldjs/should.js/commit/c17cd50777e49a556381ef71bac69d1e98255012) has been removed. Now [should#containEql](https://github.com/shouldjs/should.js#containeqlothervalue) is available.
  * [sinon](https://www.npmjs.org/package/sinon), [rimraf](https://www.npmjs.org/package/rimraf), [async](https://www.npmjs.org/package/async) and [hashdir](https://www.npmjs.org/package/hashdir) are unused.
* I fixed .npmignore.
  * `.DS_Store` and `node_modules` are ignored by default. See the npm developer guide, [*Keeping files out of your package*](https://www.npmjs.org/doc/misc/npm-developers.html#keeping-files-out-of-your-package).