DOC: Update example images in README

[KCollins]

...and figure out if there's a way to embed them in pypi description.

[KCollins]

Possible default date: See Fig 2b of https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2019SW002427 for good examples of IP shocks. (cite!)

[KCollins]

Example code with events for magfig():

import datetime
events      = [{'datetime':datetime.datetime(2016, 6, 23, 20, 46, 33),'label':'Northern Jet'}]
events += [{'datetime': datetime.datetime(2016, 6, 23, 23, 21, 54),'label': 'Equatorial Jet'}]
# magfig(parameter='Bx', start=datetime.datetime(2016, 6, 23, 20, 15), end=datetime.datetime(2016, 6, 23, 21, 46), maglist_a=['upn', 'umq', 'gdh', 'atu', 'skt', 'ghb'], maglist_b=['pg0', 'pg1', 'pg2', 'pg3', 'pg4', 'pg5'], is_displayed=False, is_saved=True, events=events, event_fontdict={'size': 20, 'weight': 'bold'})
magfig(parameter='Bx', start=datetime.datetime(2016, 6, 23, 20, 15), end=datetime.datetime(2016, 6, 24, 0, 30), maglist_a=['upn', 'umq', 'gdh', 'atu', 'skt', 'ghb'], maglist_b=['pg0', 'pg1', 'pg2', 'pg3', 'pg4', 'pg5'], is_displayed=False, is_saved=True, events=events, event_fontdict={'size': 20, 'weight': 'bold'})
magfig(parameter='By', start=datetime.datetime(2016, 6, 23, 20, 15), end=datetime.datetime(2016, 6, 24, 0, 30), maglist_a=['upn', 'umq', 'gdh', 'atu', 'skt', 'ghb'], maglist_b=['pg0', 'pg1', 'pg2', 'pg3', 'pg4', 'pg5'], is_displayed=False, is_saved=True, events=events, event_fontdict={'size': 20, 'weight': 'bold'})
magfig(parameter='Bz', start=datetime.datetime(2016, 6, 23, 20, 15), end=datetime.datetime(2016, 6, 24, 0, 30), maglist_a=['upn', 'umq', 'gdh', 'atu', 'skt', 'ghb'], maglist_b=['pg0', 'pg1', 'pg2', 'pg3', 'pg4', 'pg5'], is_displayed=False, is_saved=True, events=events, event_fontdict={'size': 20, 'weight': 'bold'})