Fixed: unsigned delegate methods of CPTokenField erased by CPTextField

Previously, the unsigned delegate methods _implementedDelegateMethods was erased by the CPTextField, so some delegate methods didn't work any more.
This PR just renames the unsigned delegate methods to _implementedTokenFieldDelegateMethods.
Added: added unit test for CPTokenField
Fixed: removed unsued code in CPTokenFieldTest
Merge pull request #2135 from Dogild/TokenFieldDelegate

Fixed: unsigned delegate methods of CPTokenField erased by CPTextField