(12 Nov 2019): global configs
- BREAK: drop Python-3.6 compatibility.
- FEAT: Use (possibly multiple) global configurations for all networks,
stored in a :class:contextvars.ContextVar. - ENH/BREAK: Use a (possibly) single
execution_poolin global-configs. - feat: add
abortflag in global-configs. - feat: add
skip_evictionsflag in global-configs.