Reviewing pull requests

[Julien Le Dem <ju...@twitter.com.INVALID>]

Based on the feedback and discussion during the last Parquet syncup, I
started a doc to help with the process:
https://github.com/apache/incubator-parquet-mr/pull/23

The idea is:
 - identify who has specific expertise on certain parts of the project
(ProtoBuf, Thrift, Avro, tools, ...)
 - clarify what is expected of a committer
 - have some guidelines on what to do with incoming pull requests.
 - help with bringing PRs to the attention of the right people.

*Could you take a look at the doc included in the PR:*
https://github.com/julienledem/incubator-parquet-mr/blob/committer_doc/dev/COMMITTERS.md

If this is fine for everybody, I'd need each one of you to review:
 - what they consider their expertise on the project (they are one of the
go-to committers for that part)
 - what their github ID is (to easily mention them in such PRs)
 - it is OK to not have an expertise listed. Being an expert at something
or even a committer is not required to review a PR. This is for helping
reviewers to mention the right people in the PR when something requires
particular attention.