Enable diffrent INIT name

[boazhoch]

@mheiber
Enable diffrent INIT name.
what i mean is that - the machine requires a INIT property that holds reducer,
i want to be able to initialize the machine with other property name.
e.g
reduxStateMachine.createMachine({ INITNAME: fn(), nextStatus: fn() })

[mheiber]

I feel a little bit silly for publishing a 12-line library, the state machine thing is more of a pattern. You can just do this:

const fetchUsersReducer = (state, action) => {
    switch (state.status) {
    case 'BEGIN':
        return initReducer(state, action)
    case 'IN_PROGRESS':
        return inProgressReducer(state, action)
    default:
        return initReducer(state, action)
    }
}