Reproduce graphs from original data

[krlmlr]

Done by inst/getdata.R, I have trouble recreating yeast and USairports .

• The Nature publications required for yeast are not found, cannot open URL 'https://www.nature.com/nature/journal/v417/n6887/extref/nature750-s1.doc': HTTP status was '404 Not Found', new location linked at https://www.nature.com/articles/nature750#Sec8
• USairports relies on ~/Downloads/1067890998_T_T100D_SEGMENT_ALL_CARRIER.csv

@gaborcsardi: Can you help with the .csv file?

Moving forward, I propose to separate the downloads from the creation of the graphs so that we're less reliant on external data storage here.