Added vec IO tests for #104 (#480)

* Added vec IO tests for #104

* Added Vec test case for Reg of vecs

* Change Vec creation to check if gen is lit (and hence needs to be declared)
Fixes #104

* Fix tests (add IO())), Vec.fill()

* Fix deprecated usage.

* Add Binding IO() NPE fix so tests pass.

* Fix style - use space consistently.

* Fix style - use space consistently.