Run towncrier and bump version to 0.15.0 for release

Run towncrier and bump version to 0.14.1 for release

Run towncrier, copyedit README/docs, and bump version to 0.14.0 for r…

…elease

Run towncrier and bump version to 0.13.0 for release

stop test_cancel_sleep from deadlocking and less dependent on timer

No need for `raise Exception` because we already assert the flag.

fixes #103

Reconstruct some release history

* Test failure workarounds

* New release

* Fix deprecation warnings
* Fix cross-references in doc

YAPF'd

Version 0.9.0