Requirements: Allow python-dateutil <2.9 (rather than fixed 2.6.1)
Requirements: Allow python-dateutil <2.9 (rather than fixed 2.6.1)

Requiring python-dateutil as precisely 2.6.1 broke on Python 3.7
systems (2.6.1 is not available on those systems, apparently).

2.8.x should work ok (tested and works).

fyookball/electrum,fyookball/electrum,fyookball/electrum