tests(cucumber): add certification

adds certification cucumber test

end2end-tests/cucumber-features/balance_transfer.feature

+Feature: Balance transfer
+
+  Scenario: If alice sends 5 ĞD to Dave, Dave will get 5 ĞD
+    Given alice has 10 ĞD
+    When alice sends 5 ĞD to dave
+    Then dave should have 5 ĞD