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