No alert when installed without WooCommerce active

[MillerMedia]

Although it is obvious in the title of the plugin, if you activate this plugin without having WooCommerce active, nothing happens and you can't access the setting screen.

A WP Admin notice saying:

"Your activated One-Off Emails for WooCommerce requires WooCommerce to be active on your site."

in the instance where this plugin is active but WooCommerce is not present (either not installed or not active). For that notice, let's add a link to WooCommerce (http://wordpress.org/plugins/woocommerce) and make the notice dismissable.