Version 1.6.1: Platform fixes

This version provides a few fixes for special cases, such as mixing with `Windows.h` and better defaults
for systems like Hunter. The one new feature is the ability to produce "branded" single file output for
providing custom namespaces or custom macro names.

* Added fix and test for including Windows.h [#145]
* No longer build single file by default if main project, supports systems stuck on Python 2.6 [#149], [#151]
* Branding support for single file output [#150]

[#145]: https://github.com/CLIUtils/CLI11/pull/145
[#149]: https://github.com/CLIUtils/CLI11/pull/149
[#150]: https://github.com/CLIUtils/CLI11/pull/150
[#151]: https://github.com/CLIUtils/CLI11/pull/151
This tag has no release notes.