add hydrograph plot function
closes #15 (closed)
example code:
siteno = '06892350'
df, _ = dataretrieval.nwis.get_dv(site=siteno,
parameterCd='00060',
start='2019-01-01',
end='2020-01-01')
ax = hyswap.plots.plot_hydrograph(
df, data_col='00060_Mean',
title=f'2019 Hydrograph for Station {siteno}',
ylab='Streamflow, in Cubic Feet per Second',
xlab='Date', yscale='log')
plt.tight_layout()
plt.show()
resulting plot: