synapsestudios/synapse-base — pull request #114 by synbot (2014-08-27 04:15:57+00:00)
Title: Add RowNotExists Validator

## Add RowNotExists Validator

### Acceptance Criteria
1. `RowNotExists` validator constraint exists.
1. Works just like `RowExists` constraint but returns `false` rather than `true` if the row exists.

### Tasks
- Create validator and constraint.

### Additional Notes
- None