Update CI settings for faster build / Update package.json

* I updated the CI setting files.
  * Adding `sudo: false` enables [container-based build on Travis CI](http://blog.travis-ci.com/2014-12-17-faster-builds-with-container-based-infrastructure/).
  * Clones repository *shallowly* for faster download.
  * [Caches `node_modules` directory on AppVeyor](http://www.appveyor.com/docs/build-cache).
* I updated SPDX license type and license file URL in package.json.
  * The license of this project has been changed from e418be967f952a20f5bf137be7b289e0b859fae1.
* I removed `--reporter` option from the `mocha` commands on test scripts.
  * The current version of Mocha uses the spec reporter by default.
* I updated image format of the AppVeyor badge from PNG to SVG. SVG badges look beautiful on retina displays.

| PNG ver. | SVG ver. |
|---|---|
|![Build status](https://ci.appveyor.com/api/projects/status/r5vung2ipn9uj4sy)|![Build status](https://ci.appveyor.com/api/projects/status/r5vung2ipn9uj4sy?svg=true)|