Add support for passive Nagios checks

Hi there,

this is an attempt to add support for passive Nagios checks. Depends on http://github.com/bracki/clj-nsca which in turn depends on https://code.google.com/p/jsendnsca/.
Only supports [three](https://jsendnsca.googlecode.com/svn/jsendnsca-docs/javadocs-2.0.1/com/googlecode/jsendnsca/encryption/Encryption.html#enum_constant_summary) encryption methods (or rather one ;p). `NONE`, `XOR`, `TRIPLE_DES`.

```clojure
(def nag (nagios "localhost" 5667 "top-secret" :TRIPLE_DES))

(streams
  (default {:state "ok" :description "some desc"}
   nag))
```
Cheers,
Jan