@membrane/util v0.7.3

Goals

• Shared between client and server (and thus not in avya-common)
• Write a fully immutable version of Ref (should I use immutable.js?)
• Write a consistent version of SchemaTraversal. And RefTraversal?
• Use flow on all files. Export types
• Test as much as possible so that I can work on a solid foundation

Modules

• Ref. Use Immutable.js so that we don't need a RefBuilder
• SchemaTraversal. Same as old one but with a consistent interface
• RefTraversal. Traverses a ref through a schema.
• Ref normalization/denormalization? Possibly