AnushaPB/wingen: wingen 2.1.1

First CRAN release! Minor changes made for CRAN.

Switch to ggplot() in examples and preview_gd()

• Switch from using base R plotting with plot_gd()/plot_count() to ggplot plotting with ggplot_gd()/ggplot_count() in the README, vignette, and preview_gd() functions
• This was done to avoid modifying the users environment with par()
• plot_gd() and plot_count() can still be used

Simplification of vignette and examples

• To decrease code test time for CRAN the vignettes and the examples were reduced, however the core information remains the same