\- Added tests
\- Removed the iteritems, iterkeys, itervalues, viewitems, viewkeys, viewvalues methods
Now a call to the above methods (Python 2.*) raises NotImplementedError exception
\- Fixed the update method behaviour
Now the update method takes only one argument like the built-in dict type
\- Changed the behaviour of the items, keys, values methods to mimic the behaviour of the equivalent Python3 methods