[WIP] Release 0.5.3

Last one from the milestone bucket, then onwards and upwards to some newer stuff:

 - [x] update release notes
 - [x] publish to MyGet
 - [x] sanity test updates
 - [x] :shipit:

Once this is out, I'll look to do a version with the latest stuff in `master` mid-next week and bump it to 0.6.x