Constrain version of eliot to match setup.py.
We currently require ssh at runtime, so specify that dependency.
Add explict dependency on zope.interface.

We use it directly, so specify the dependency explicitly in the RPM.
Make setuptools version in RPM match setup.py.
Merge pull request #948 from ClusterHQ/rpm-fixes

Fix RPM dependencies.

Resolves FLOC-969.