Update README.md

[skip ci]
Wording [skip ci]
Remove sugar_target_add_framework
Remove old

Substitude sugar_add_definitions_{debug,release} and
sugar_target_add_definitions with target_compile_definitions
Update minimum version to 2.8.11
Add boost stub [skip ci]
Fix build
Remove sugar_mark_macosx_resources
Use patched cmake version
Merge branch 'update' into update.macosx