Release for libsass 3.2.0

https://github.com/sass/libsass/releases/tag/3.2.0

• Update to latest libsass release (3.2.0)
• Add options for remaining output styles
• Add indent and linefeed config options
• Add benchmark option to command line tool
• Add watcher option to recompile on changes
• Refactor for libsass context option initializing
• Expose resolve_file function on the C-API
• Add experimental API for multiple importers
• Add highly experimental API for custom headers