v0.2.1 ld-signature

• fix: merge issue-release plugin 1a7e983e798a057

• fix: merge issue 73f32484e9857dd

• minor release 0.2.1 d0309e4dbeb75fd

• fix: Make test keys static. c173913d9837581

• chore: Upgrade test framework. 6825a0c9c87baaf

• chore: Manage guava dependency. a268fa2d0a2fd84

• chore: Use jsonld-java 0.12.3. f2fdd331897bd98

• chore: Change source version from 1.7 to 1.8. a1d27bbb577870b

• chore: Add unit tests for EcdsaSecp256k1Signature2019. 49d78c8e6e42fe7

• docs: Update README to match latest code. bbd46e93e386a05

• fix: Use hardcoded test keys. f3dbb81076d331d

• fix: For now, remove unsupported JSON-LD 1.1 features from security context. fe26808c11b40c5

• fix: Change curve name from P-256 to secp256k1. 0bf14dc15b9ed56

• chore: Upgrade nimbus-jose-jwt dependency. 53b2b3e61bf987e

• fix: Use jsonld-java 0.13.1-SNAPSHOT. ef1460d2bc14b19