pty is too quick to send shell input -- remove superflous prompt trigger
pty is too quick to send shell input -- remove superflous prompt trigger

This closes #166

luis-rr/saga-python,mehdisadeghi/saga-python,mehdisadeghi/saga-python,luis-rr/saga-python,telamonian/saga-python,telamonian/saga-python,luis-rr/saga-python