Improve the parallel coordinate plot code

[lee1043]

• Added parameters to enable label for violin plot in legend and to allow more of customization of the legend box
• Minor clean up for less print on screen
• Regenerated example plots using the latest code and data

[kristinchang3]

Hi Jiwoo,

This looks great! The only error I ran into was for adding the watermark to any example images: rotation was set to a string of '25' instead of an integer 25. I went ahead and removed the quotations. Otherwise, these look great!

[lee1043]

@kristinchang3 thanks! I am merging the PR.