message: updated changelog for version 1.2.1
diff: # Change Log
  -## [1.2.0](https://github.com/onqtam/doctest/tree/1.2.0) (2017-05-16)
  +## [1.2.1](https://github.com/onqtam/doctest/tree/1.2.1) (2017-05-24)
  +[Full Changelog](https://github.com/onqtam/doctest/compare/1.2.0...1.2.1)
  +
  +**Closed issues:**
  +
  +- Compile error under MSVC 2015/2017 if \<thread\> included in same file as "doctest.h" [\#72](https://github.com/onqtam/doctest/issues/72)
  +
  +**Merged pull requests:**
  +
  +- docs: TEST\_CASE\_METHOD -\> TEST\_CASE\_FIXTURE [\#71](https://github.com/onqtam/doctest/pull/71) ([akrzemi1](https://github.com/akrzemi1))
  +
  +## [1.2.0](https://github.com/onqtam/doctest/tree/1.2.0) (2017-05-15)
  [Full Changelog](https://github.com/onqtam/doctest/compare/1.1.4...1.2.0)
  **Closed issues:**
  