[Webpage update] New Slides

[Matthias J. Sax-2]

Hi,

I just opened a PR that updates the list of slide in the "Materials"
page. I browsed slideshare profiles I am aware of and added everything I
thought it might be interesting, while not being too repetitive.

Additionally, I linked dataArtisan's slideshare profile and Flink
training material, Flink Forward Talks, and FlinkBigData.com

Please let me know if I missed an important slide deck and/or if I
should remove anything:

https://github.com/apache/flink-web/pull/13

Otherwise, please let me know if you are ok with it, so it can get merged.


-Matthias