First stab at a minecraft_plugin lwrp.

It is only useful when your install_type is set to bukkit. If anyone
knows of plugins for vanilla minecraft, feel free to create a issue
with a link, and I'll look into adding support.

minecraft_plugin 'http://foobar.com/MyPlugin.jar' will place
MyPlugin.jar in your minecraft/plugins directory, and restart the
service. Currently only works if the plugin is a jar file. It still
needs to learn about archives, mainly zip files from what I have
seen.
Fix rubocop warning in provider