Fixes #226: atomic operations and transaction support in AR.
Fixed typo in internals/ar.md.
AR atomic scenarios fixes.
AR atomic scenarios internals doc fix.
isOpAtomic → isOperationAtomic
Better argument name in the ActiveRecord::isOperationAtomic() method.
Merge pull request #253 from resurtm/ar-transactions-3

Fixes #226: atomic operations and transaction support in AR.