v1.6.0

• add a notice that pypi2nix (for now) only works with latest unstable channel
• -E/--extra-build-inputs option is now documented in README.rst, #93
• Add support for "-e git+" resources in requirement files
• pypi2nix can now build scipy/numpy, looks examples/ folder how to make it work, #84
• building all examples also on darwin platform
• setting SOURCE_DATE_EPOCH to a value after 1980, #87
• provide nicer error when http like requirement is present
• --setup-requires option to install pip packages before building wheels, #82
• -E/--extra-build-inputs can now be specified multiple times
• include nix as a dependency of pypi2nix since nix-shell is used in stage1