Switch to chai assertion library
First test for bag data structure
Add bag function
Tests for bag api
Add add method
Add isEmpty method
Add size method.  Remove parameter on isEmpty.
Fix bag tests
Return bag methods
Add test for internal array on bag
Rename internal array on bag
Rename internal array on bag
Return array of items
Make array defined test more specific
Add test for testing add functionality
Add add functionality on bag
Test for adding more than one item into bag
Add test for isEmpty functionality on bag
Fix object missing on isEmpty test for bag
Add functionality for bag isEmpty()