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.
You've inversed the meaning of the sentence. run-time errros were reported as client errors. now they are correctly reported as run-time errors.