Test improvement, shows _targetClass camelCase bug

There is an issue where setting _targetClass on hasAndBelongsToMany
relations with a camel-case model name, fails.

Signed-off-by: Khashayar Hajian <me@khashayar.me>
Fix camel-case issue where relation is 'hasAndBelongsToMany' #304

Signed-off-by: Khashayar Hajian <me@khashayar.me>
Merge pull request #303 from khashayar/feature/test-improvement

Test improvement, shows _targetClass camelCase bug