Update CONTRIBUTING.md
Link BitHub payout image to blog post

As in WhisperSystems/TextSecure#591
Merge pull request #95 from backspace/link-to-bithub-post

Link BitHub payout image to blog post
adding version information in
sketching
closer to what I'm looking for
removing support for unencrypted pipeline
architecture done
tests passing
Merging back with Christine's protocol buffer changes