(maint) Fix yaml install prefix

Previous version put yaml-cpp at C:\ instead of $(prefix).
Merge pull request #22 from MikaelSmith/fix-yaml-install-prefix

(maint) Fix yaml install prefix
(maint) Select Boost static linking against cfacter

Native facter project changed Boost linking to be dynamic by default, and
require an option to use static linking. Use static linking on Windows.