Changes to poster and added poster as an image.

[greleigh]

Thanks! I just committed some proposals:

• I think width=40% is sufficient (feel free to change if you disagree)
• Made image into link to full-size poster
• missing word
• fix case of line-break between math-mode & punctuation

Can you upload a higher quality image? It can be in addition to poster.png and can be used for the full image link.

[feffemannen]

Thanks!

I added a pdf and changed the link to the pdf.