Define variables can now be specified to a SystemVerilogTarget via the defines argument. This can be a convenient manner to pass arguments into existing verilog code.
Added a test for the while loop functionality in fault (tests/test_while_loop.py)
Added support for UnaryOp to SystemVerilogTarget.
Added wait_until_high/wait_until_low/wait_until_posedge/wait_until_negedge into the Tester. These are not implemented as actions but instead are built from the _while() and step() commands.
Depends on pull request #139