Add Expr.in.
Add Toy.termHasRightVariable.
Change Toy.termHasRightVariable to Toy.termGetRightVariable.
Add Expr.leftNeighborPath.
Add Expr.walkPatterns and Toy.varFactorCounts.
Extend catchResult, add throwResult.
Improve message again.
Rename freeNames to freeVars.
Add Toy.termLeftThan.
Add rules.placeTermLeftward.
Add Expr.rightNeighborPath.
Add Path.upTo and Expr.matchSchemaPart.
Fix test.
Reimplement and rename moveLeftTerm to moveTermLeft.
Reimplement and rename rules.moveTermRight.
Support rule "test" property as a way to check rule offerability.
In rules.moveTermRight, fix some of the facts; move facts to the ruleData.
Clean up rules.moveTermRight.toOffer.  Fix rules.moveTermLeft.
Add Toy.matchFactPart.
Small bug fix.