Feature/lwrp

This is the start of discussing an LWRP for configuring logstash instances. The idea is to make the cookbook less complicated by using its own LWRP and also to require less customization for non-standard installs.

Note that the `instance` LWRP doesn't concern itself with services or templates or anything else. Its job is simply to lay down the basics - create the appropriate users, make directories and install a jar file. The service stuff is up to the recipes surrounding this.

Right now this is tested and working using the `jar` install method

In my mind, the server and agent cookbooks reduce clutter and simply perform:

`logstash_instance "agent"`

or

`logstash_instance "server"`

along with the logic for config files

Other LWRPs are appropriate in the future but for now this is a start.