candlepin-common rpm

So we have an initial cut at building the candlepin-common rpm in brew. The Fedora build does not yet work because we have some packages to build in Fedora or we'll have to resurrect candlepin-deps. I'm trying to avoid doing that. For now, let's focus the review on the brew portion.

TEST
------
* Build a a SRPM using tito
```tito build --test --srpm```
* Do a scratch build in brew
```brew build --scratch candlepin-1-rhel-6-candidate /path/to/candlepin-common-SRPM```


Shouldn't need this exclude in common.