Consider and explore redux-style reducer approach for stats

[cabiad]

I tend to agree that following the stats flow through the code is a little unclear. Maybe this would help.

See #1 (comment)

just a random comment: what about exploring a redux-style reducer approach for stats, where a visitor would receive the node and the top-level stats tree as arguments and return a new stats object?

[cabiad]

see also #1 (comment)

just a random comment: what about exploring a redux-style reducer approach for stats, where a visitor would receive the node and the top-level stats tree as arguments and return a new stats object?

@francoiscampbell yeah I like the redux idea. Although this breaks the ast.NodeVisitor api compatibility. I'm not sure how much we desire this compatibility as a feature though