Tests enhancements for Rules functionality

Per #21 this merge adds tests for the following rules:
- ruleIsNineByNine
  - Checks that dimensions of puzzle are 9x9
- ruleOnlyNumbersOneThroughNine
  - Checks that no numbers other than [1-9] are present
- ruleRowsHaveOneThroughNine
  - Checks that every row has all digits in [1-9] at least once
- ruleColsHaveOneThroughNine
  - Checks that every column has all digits in [1-9] at least once
- ruleNoDuplicatesInRow
  - Checks that no row has duplicate numbers (empty space exempted)
- ruleNoDuplicatesInColumn
  - Checks that no column has duplicate numbers (empty space exempted)

It also includes function stubs for each rule, added in cdcaf60. Implementation of these rules is still pending. TDD FTW :+1: 

**NOTE**: Puzzles used in tests for rules have been defined in the qUnit `module.setup` callback to make them easy to use in all rule tests.