Added new tests:
1) should be able to do a set deep attribute with array of attributes
2) should be able to set new deep property of model
3) should be able to set deep attribute with deep array of attributes
4) should fire change event upon some deep attribute gets changed
5) should fire change event upon some nested attribute gets changed
6) should be able to change deep attribute without firing of change event
7) should be able to unset deep attributes
8) should be able to unset deep array of attributes (reverted from commit 351ac40d97aa618633c57a956cef9927d265b1b5)