modified list/cloud facets to inherit by invoking superclass
constructor instead of explicitly invoking .extend
refactored list/cloud/enumerated facets to improve code reuse
made facet._configure an instance method for enumerated facets
continued refactoring enumerated/list/cloud facet
finished refactoring enumerated/list/cloud facet
Merge pull request #118 from karger/2014-12-29_facet_refactor

Refactored cloud and list facets into enumerated facet