Merge pull request #7 from openFrameworks-cpp11/cpp11

feature-add osx-clang-libc++ flavour to forumulas
updated libpng download link, closes #8
Merge branch 'master' of github.com:danomatika/apothecary
Merge branch 'master' of github.com:danomatika/apothecary into add-git

Conflicts:
	scripts/apothecary/formulas/cairo/depends/libpng.sh
update README to match with new functions
avoid unset variables errors