Draft NOTES for 1.13.0

@mglukhovsky can you please review?

@danielmewes @Tryneus @mlucy @danielmewes @neumino @srh Please also take a look to make sure I haven't mis-characterized some of your fixes.
The highlights of this release are the r.http command for external data access, change feed support via the new r.changes command, and full support for Node.js promises in the JavaScript driver.