Release version 0.6.0-alpha3.
Continue development on 0.6.0.
Load task-side the same namespaces loaded locally.

In order to support libraries of common task functions, we need some mechanism
to ensure that Parkour loads all necessary namespaces for a particular task,
such as those providing de/serialization multimethod & protocol implementations.
This implementation defaults to loading the same set remotely as are loaded
locally, but allows users to override as necessary for particular jobs.
Add tests for parkour.toolbox functions.
Add and test `bound-reducers-split` cstep.
Modernize source shape tests.
WIP; Updating documentation for 0.6.0.