yaws: v1.96 +HEAD - Update yaws formula with v1.96 plus --HEAD option 

Changes include:
* Update release from 1.94 to 1.96 in yaws formula using GitHub's releases URL
* Update `sha1` for new source archive
* Provide `--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
* 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

Note: the current `yaws` formula fails the the following error when Erlang version is R16B01 or above:

```
compile: warnings being treated as errors
yaws_websockets.erl:1250: crypto:sha/1 is deprecated and will be removed in in a future release; use crypto:hash/2
make[1]: *** [../ebin/yaws_websockets.beam] Error 1
```

This pull request will fix that.