Sync from master

Fixes the bullet points in the proto README.md

Adds the common protos along with a README.md

Fix typos, grammar and broken link.

Actually Fix broken link to helloworld.proto

Updating private fork to grpc master.

Fixed 2 typos.

Jayantkolhe patch 1

Fixed 2 typos.

Update Step_2.md

Update Step_1.md

Move from codesite.

Update README.md