first pass at collapsing receiver and outlet binaries

Currently there are 3 bins: l2met, librato_outlet, and graphite_outlet. Ideally there is only 1 binary that accepts flags as to which service to start. Something like:

```bash
$ ./l2met -receiver -librato
```

This command would start a single UNIX process and it would receive logs in addition to outleting metrics to Librato. This path still makes process distribution possible:

*machine a*

```bash
$ ./l2met -receiver
```

*machine b*

```bash
$ ./l2met -librato
```