Revert "Change indentation of `package.json` to 4 spaces."

This reverts commit fc9f34d7f0c6cfce203044ac5aaa77b1e33b125b. It seems
that `grunt-release` also modifies the indentation of `package.json`.
Revert "Don't explicitly label the MIT license."

This reverts commit 4cc164c4ab2ba31e85c57bbb8139b442b23c9516.
Convert license to Markdown.
Alphabetical order.