adding the ability to add admin and other users to mongodb through recip...

...e, readme updates, kitchen integration tests
adds
- user_management recipe, which will require auth on mongo config
- user resource
- user provider
- users attributes
- user_management integration tests
I removed the one from dbconfig.rb, it was superfluous. These attributes are not included if you don't include the recipe, and this recipe doesn't run any other recipes. I could make it include the default but wasn't sure if it was really necessary.