message: Prepare changelog for v0.12.4
diff: +Changes in [0.12.4](https://github.com/matrix-org/matrix-react-sdk/releases/tag/v0.12.4) (2018-05-16)
  +=====================================================================================================
  +[Full Changelog](https://github.com/matrix-org/matrix-react-sdk/compare/v0.12.4-rc.6...v0.12.4)
  +
  + * No changes from rc.5
  +
  Changes in [0.12.4-rc.6](https://github.com/matrix-org/matrix-react-sdk/releases/tag/v0.12.4-rc.6) (2018-05-15)
  ===============================================================================================================
  [Full Changelog](https://github.com/matrix-org/matrix-react-sdk/compare/v0.12.4-rc.5...v0.12.4-rc.6)
  