FileUtils#copy_metadata: update comment, version
Update yaws formula with newer release and --HEAD option

Changes include:
* Updating release from 1.94 to 1.96 in yaws formula
* Providing --HEAD option for yaws formula (needed for newer Erlang versions)
* Add `test` method with a basic tests for yaws formula
* Revert private method extraction to address method extraction from @adamv
* Update url and sha1 to GitHub release 1.96 tar.gz
* Use autoconf for yaws formula and specify build dependency on autoconf
* Add patches for yaws formula which is necessary for Erlang R16B01 and above
* Make tests valid for --HEAD builds even when the next version is bumped