fix bug 1055268 - Package Socorro

Adds the ability to package an *rpm* of Socorro while not disrupting *tarball* creation.

This can be done in bash by
```bash
$ export BUILD_TYPE=rpm
$ socorro/scripts/build.sh
```

There is also a `make` target for package, but like the install target, it will not work without first exporting environment variables.
I don't understand adding it to ```.PHONY``` if it's not used yet can you explain that?