Fixed problem with lack of reporting of failed tests (#62)

* Fixed problem with lack of reporting of failed tests
Add comments on Driver.execute methods
Made Driver.apply use underlying execute methods and provide a couple more useful
options it can set: verbose and testerSeed.  It should be default way of invoking tests
unless need for more backend toolchain option control pushes user towards execute methods
Add step number to expect messages
Fixed number of successful expects not be counted in interpreter based tester
Failed expects print even if verbose is off
Fixed type shadowing on PeekPokeTester peekAt

* Fix typo in comment