New features
GAM visualization
plot_gam and plot_gam_check for visualizing marginal effects of 1d smooths from mgcv models.
plot_gam_2d and plot_gam_by do the same for 2d smooths and 1d with 'by' option
plot_gam_3d takes plot_gam_2d to 3D with interactivity (via plotly)
Misc other
corr_heat does 2 and 3d heatmaps of correlation matrices.
color_contrast_checker checks foreground and background colors for web accessibility.
col2hex takes an R color and produces the associated hex value.