FluidCommand is a command library intended to make it easy to create sub commands for your bukkit plugin.
It is intended to be bundled with your plugin so it does not require the installation of another plugin on the server.
For more information, please have a look at the github page: https://github.com/muuknl/fluidcommand. Here you can also find the installation instructions if you want to use maven to manage your dependencies (which I encourage!). Otherwise, you can download the jar from this page and include it in your build path.