Initial commit: app structure, initial docs and wip on api.
docs: fix config vars in readme.
docs: add url and tweak formatting.
work: added impl notes on the worker / retry algorithm.
work: boilerplate to configure a console script.
work: wip impl of redis consumer.
work: refactor and blind implement task performing.
model: rename task manager method to `reschedule`.
model: tweak typo and unpacking in DueFactory.
model: remove constants from orm.__all__ list.
work: add comment above reschedule.
docs: add notes to readme.
task: store and pass through headers.
api: refactor task manager to encapsulate task data.
due: make request exc backoff alg configurable.
work: tweak kwarg and max delay in task performer.
work: lose notes to self docstring.
tests: ftests for task performer.
docs: add impl note to readme.
api: add exc to tree module pending refactor.