Flaming flim-flammery

This is a major release of re-graph due to the API signatures changing.
You are strongly advised to read the UPGRADE guide for rationale and code examples.

This release changes:

• Nearly all API signatures, rationalising multiple positional args into a single map. The legacy API is retained, for the time being, at re-graph.core-deprecated #81

This release improves:

• Documentation of options for authentication #80
• Error messages when re-frame is not initialised properly #86