Clojure wrapper for Neo4j, a graph database.

See project page (http://github.com/wagjo/borneo) for usage instructions,
documentation and examples.

Notes:
- Using official Neo4j bindings.
- Not using Blueprints interface.
- neo-db holds the current db instance, so that users do not have
  to supply db instance at each call to db operations. This approach has
  of course some drawbacks , but I've found it suitable for my purposes.
- All mutable functions are by default wrapped in transactions. That
  means you don't have to explicitly put them in transactions. The Neo4j
  transaction model allows for fast transaction nesting, so you can easily
  have your own transaction if you have a group of mutable functions.
  In that case just wrap your functions inside with-tx.
- NullPointerException is thrown if there is no open connection to the db.