Add install-only recipe

Added functionality to only create zookeeper user and install files with
a new recipe 'install' which is just a subset of the default recipe.
The default recipe continues to work as it did before.

Signed-off-by: Scott Lovenberg <scott.lovenberg@gmail.com>
Should also feature a consistent header to go with the other recipes, e.g., the first few lines should be:

```ruby
# recipes/install.rb
#
```