Use `html-minifier` to also minify the inline JS

In `v0.6.0`, `html-minifier` introduced the ability to minify
JavaScript (via the `minifyJS` option), thus, removing the need
to use `htmlcompressor`.

Ref: https://github.com/kangax/html-minifier/blob/911bf378f6fca170a83c3876b435a94d9316c03b/CHANGELOG.md#060

Close h5bp/html5boilerplate.com#117.