ver bump

CHANGELOG.md

-# v2.14.19
-
-* `memoize` will release the per-function lock while calling target function
-* also fixed docs for `memoize`
-* added `cache_memoize`
-* added `hashables_to_int`
-* added covariance to hashable for `satella.coding.typing.K`
+# v2.14.20

satella/__init__.py

-__version__ = '2.14.19'
+__version__ = '2.14.20_a1'