Update README.md

updated version in dependency example,
Merge pull request #2 from shezarkhani/master

Update README.md
Updated version of protoc compuler to be compatiable with newer maven.

Added null branch to Datum encoder.
Made some changes based on static code analysis
Updated proto file from most recent RethinkDB Git ( e9be56973ce34f917965116d7ad7eceb47e8c9c2 )
Merge remote-tracking branch 'upstream/master'