feat: upgrade to local did resolver (#48)

* feat: upgrade to local did resolver

* refactor: export resolver so it can be mocked in tests

* wip: refactor tests to remove dependency on uport and nacl did resolvers

* test: fix tests to verify pregenerated JWT

* test: fix hard coded jwts for validFrom timestamp tests

* test: fix  remaining

* test: add tests for normalizeDID

* refactor: upgrade ethr-did-resolver to fix imports

* refactor: rename variables and clean up async syntax for tests