Add support for 'wp option patch' to be able to add, update and remove nested values in options too

[JohnEricson]

Hi @BronsonQuick! Here is the pull request that adds support for the new wp option patch functionality in WP-CLI that I mentioned in #141. This is a very straight forward modification of your code. I've simply added a new wp::option::patch type that is basically a copy of your wp::option type with some modifications. Here is an example of how it's used:

  wp::option::patch { 'my_array':
    ensure   => 'equal',
    key_path => 'my_key_in_array',
    value    => 'my_new_value',
    location => $wp_install_dir,
  }

I've verified that all operations (present, equal and absent) works fine on both Linux and Windows and I'm already using this to manage my WordPress installations.

I'd really like to have this merged to your repo. If you have any questions or suggestions just let me know 🙂