Add release notes

[david4096]

Changes to ga4gh/schemas master branch since version 0.6.0a7 (Aug 19, 2016)

• Introduced G2P API endpoints including the following:
  • POST /phenotypeassociationsets/search
  • POST /phenotypes/search
  • POST /featurephenotypeassociations/search
  • Add biometadata to RNA quantifications
  • Add protobuf based HTTP annotations

Improve display of older note slightly. close #718

[bwalsh]

+1