Factor out Pigosat.isReady() guard from all methods
Factor out Pigosat.isReady() guard from all methods

Similar to @justinfx/pigosat@a755660037d2fe1b1d414413229e899b65b79bb4
but use simpler syntax in isReady function (boolean expressions return a boolean
value) and call it isReady rather than isValid because there's already the
NotReady status constant.

justinfx/pigosat,justinfx/pigosat,wkschwartz/pigosat,wkschwartz/pigosat