message: Chore: update CHANGELOG.md for next release.
diff: +## X.Y.Z (INSERT_DATE_HERE)
  +
  +#### Major Changes
  +- [Support string Literals as Token patterns.](https://github.com/SAP/chevrotain/issues/431)
  +- [Lexer Performance optimizations 0.27.0](https://github.com/SAP/chevrotain/issues/432)
  +
  +
  +
  ## 0.26.0 (3-26-2017)
  #### Breaking Changes
  