remove is_live from required parameters

for me webform_detect, now in master, does not work. any test transaction throws errors about the req. parameter is_live not being found.

i removed is_live from required params, making sure those functions provide a default, and now live as well as testing transactions work for me. stripe finds or creates customers and the result is fed back to CiviCRM.

initially a recurring contribution worked too, but i'll know by tomorrow if the second installment gets processed and sent back to civic.