support pickle to graphite.

Add support for the graphite pickle wire protocol.

There are two new configuration options related to graphite:

```
    { graphitePicklePort: 2004,
      graphiteProtocol: "pickle" }
```

If `graphiteProtocol` is configured as `pickle` then the `graphitePicklePort` is used instead of the current `graphitePort` configuration. Both `graphitePicklePort` and `graphitePort` now default to their well-known values, making them optional.

The limited implementation of the Python pickle format required for Graphite support is documented in `graphite_pickle.md`.

The tests in `graphite_pickle_tests.js` invoke a Python script to verify that the packets received over the wire are able to be interpreted. This means that a Python interpreter is expected to be in the path. We are open to discussing alternate testing options.