Corrected inconsistencies in the Javadoc.
[codec-memcache] Simplify object hierachy and remove Headers.

This changeset removes the separate message headers and merges the
field directly into the messages. This greatly simplifies the
object hierachy and also saves header allocations in the pipeline.
Ensure the HttpResponseEncoder is always placed before the HttpObjectAggregator. Part of [#2219]
Add CONTRIBUTING.md

Motivation:
We often receive a bug report or a pull request which do not give us
enough information.  If CONTRIBUTING.md exists in the repository, Github
will display some notice in the beginning of the issue submission form,
which might increase the overall quality of the bug reports and pull
requests.

Modification:
Write CONTRIBUTING.md

Result:
Potentially higher-quality bug reports and pull requests
Update CONTRIBUTING.md
Fix buffer leak in test which was introduced while implement ZLIB_OR_NONE support. Related to [#2269]
Add content length and date headers to CORS response
[#2280] Correct logic in Native.finishConnect. Fix use of optval parameter in c getOption function. In epoll event loop, check that channel is open before processing event.
Fix buffer leak in test which was introduced while implement ZLIB_OR_NONE support. Related to [#2269]
added support for empty query parameters