Issue 15 + Refactoring

I've made fairly significant changes to the class hierarchy and I'm in doubts whether they are to the better.
Please ignore the status and config part for the time being and let me know if the *Repository changes make sense. Specifically, I tried to extract common subject registration/lookup logic into AbstractSubjectValidatingRepository and succeeded for for InMemory and LocalFileSystem but with Zookeeper I was afraid to significantly alter the flow of the code and finished up using the new base class in a somewhat awkward manner. The tests pass, but I don't feel terribly good - so any comments, whether positive or negative will help :smile: 
Please ignore, like I mentioned it was not ready for merge, just to let you
judge the new hierarchy.

On Tue, Dec 9, 2014 at 9:54 PM, Felix GV <notifications@github.com> wrote:

> In
> common/src/main/java/org/schemarepo/AbstractSubjectCachingValidatingRepository.java
> <https://github.com/schema-repo/schema-repo/pull/21#discussion-diff-21585414>
> :
>
> > @@ -0,0 +1,53 @@
> > +package org.schemarepo;
> > +
> > +/**
> > + * Created by ernest.mishkin on 12/5/14.
>
> I think we should avoid auto-generated IDE headers as well as mentions to
> individual contributors. The code should hopefully be enough clean and
> self-documented that it doesn't matter who wrote it (: ...
>
> —
> Reply to this email directly or view it on GitHub
> <https://github.com/schema-repo/schema-repo/pull/21/files#r21585414>.
>