Simpleflow

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- Make the dynamic dispatcher more flexible (161)
- Fix README.rst format (160)
- Tiny command-line usability fixes (158)

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- Don't override passed "default" in json_dumps() (155)
- Expose activity context (156)

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- Improve process management (142)

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- Don't reap children in the back of multiprocessing (141)
- Don't force to pass a workflow to activity workers (133)
- Don't override the task list if not standalone (139)
- Split FuncGroup submit (146)
- CI: Test on python 3 (144)
- Decider: use workflow's task list if unset (148)

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- Refactor: cleanups and many python 3 compatibility issues fixed (135)
- Introduce AggregationException to inspect exceptions inside canvas.Group/Chain (92)
- Improve heartbeating, now enabled by default on activity workers (136)

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- Fix tag_list declaration in case no tag is associated with the workflow
- Fix listing workflow tasks not handling "scheduled" (not started) tasks correctly
- Fix CSV formatter outputing an extra "None" at the end of the output
- Fix 'simpleflow activity.rerun' resolving the bad function name if not the last event