increase ringsize to minimum 7 per DevMeeting 2018-03-04
https://github.com/emesik/monero-python/blob/0b0510654a3f19339d4b6abbf8e17a9357f4c2a9/monero/account.py#L98
` priority=prio.NORMAL, ringsize=7, payment_id=None, unlock_time=0, `