Normalize package.json.

* use https for the GitHub links
* remove the unused jquery dependency
* remove duplicate entry for contributor
* sort devDependencies by name
Update all dependencies to their latest versions.

Remove `grunt-cli` from the dependencies since the appropriate way to install it is globally.
Fix `npm run build`.

`grunt` is in PATH so there's no need to use the relative path. Fixes build on Windows.
Remove trailing whitespaces.
Enable `report: 'min'` for cssmin and uglify tasks.
Add an `npm test` script.

Maps to `grunt dev`.
Be more explicit with the `background-color` property.

Also use the shorthand `border` property when possible.