message: note about backwards compatibility
diff: @@ -8,6 +8,7 @@ Note: If you're looking for the Blockstack CLI repo it was merged with [Blocksta
  - [Profiles](https://blockstack.github.io/blockstack.js/index.html#profiles)
  - [Storage](https://blockstack.github.io/blockstack.js/index.html#storage)
  - [Documentation](#documentation)
  +- [Compatibility](#compatibility)
  - [Contributing](#contributing)
  - [Maintainer](#maintainer)
  - [Testing](#testing)
  @@ -42,6 +43,10 @@ _Note: this document uses ES6 in its examples but it is compiled down to Javascr
  [![Documentation](/docs-button.png)](http://blockstack.github.io/blockstack.js/index.html)
  +## Compatibility
  +
  +_Note:_ blockstack.js 0.14.0 and newer versions use a new on-disk format that is not backward compatible with prior versions.
  +
  ## Contributing
  This repository uses the [git flow branching mode](http://nvie.com/posts/a-successful-git-branching-model/).
  