0.2.0

Improve builders by reworking usage of context managers and adding ability to remove elements.
Features:

• Verification methods, references, and services can now be added to builders in the following manner:

  builder.verification_methods.add(...)
  builder.authentication.embed(...)
  builder.authentication.reference(...)
  builder.service.add(...)

• Verification methods, references, and services can now be removed from builders (completing the CRUD operations of DID Documents as delegated to the DIDDocumentBuilder)

Breaking Changes:

• builder.verification_methods(default_suite=...) is now builder.verification_methods.defaults(suite=...)
• Removed DIDDocument.to_builder(). Use DIDDocumentBuilder.from_doc(doc) instead.