sdk.createRegistration correctly returns a DSNPUserURI

[wilwade]

Problem

sdk.createRegistration said it was returning a DSNPUserURI, but it was not.

Solution

Made it return a DSNPUserURI

Double Checks:

• [x] Did you update the changelog?
• [x] Any new modules need to be exported?
• [x] Are new methods in the right module?
• [x] Are new methods/modules in core or not (i.e. porcelain or plumbing)?
• [x] Do you have good documentation on exported methods?