message: changelog for 2.2.1
diff: # Change Log
  +## [2.2.1](https://github.com/onqtam/doctest/tree/2.2.1) (2019-01-15)
  +[Full Changelog](https://github.com/onqtam/doctest/compare/2.2.0...2.2.1)
  +
  +**Closed issues:**
  +
  +- Make doctest work with XCode 6 and 7 \(no support for C++11 thread\_local\) [\#172](https://github.com/onqtam/doctest/issues/172)
  +- Print vector content. [\#170](https://github.com/onqtam/doctest/issues/170)
  +- Conan package [\#103](https://github.com/onqtam/doctest/issues/103)
  +- \[feature request\] Thread-safety for asserts and logging facilities [\#4](https://github.com/onqtam/doctest/issues/4)
  +
  ## [2.2.0](https://github.com/onqtam/doctest/tree/2.2.0) (2018-12-05)
  [Full Changelog](https://github.com/onqtam/doctest/compare/2.1.0...2.2.0)
  