Upgrade to 1.0.8

Concerns: pushword/conversation

A conversation form can drive its own step transition

AbstractConversationForm exposes advanceStep() (move to the next step and store the workflow) and deleteWorkflow() to subclasses. Both halves of the transition used to be private, so a form overriding validStepN() could advance but not store.

Affects forms with three steps or more that override a step validator. They answered the next POST with a 404 “Conversation workflow not found”. Replace a bare incrementStep() with advanceStep(); see the conversation doc.