Change type of enable_physics cmdline arg

myth

@@ -83,7 +83,7 @@ options.add_argument('--sync-all', action='store_true', help='Also sync contract
 options.add_argument('--max-depth', type=int, default=12, help='Maximum recursion depth for symbolic execution')
 options.add_argument('--solc-args', help='Extra arguments for solc')
 options.add_argument('--phrack', action='store_true', help='Phrack-style call graph')
-options.add_argument('--enable-physics', type=bool, default=False, help='enable graph physics simulation')
+options.add_argument('--enable-physics', action='store_true', help='enable graph physics simulation')
 options.add_argument('-v', type=int, help='log level (0-2)', metavar='LOG_LEVEL')
 
 rpc = parser.add_argument_group('RPC options')