add requirements for parseCSS and remove CoVex stuff from repo

.gitignore

netex/assets/boxplot.png

netex/assets/covex_logo.png

netex/assets/covex_logo_small.png

netex/assets/graph_example.png

netex/assets/leg1.png

netex/assets/leg2.png

netex/assets/legend.png

netex/assets/legend1.png

netex/assets/legend11.png

netex/assets/legend_main_network.png

netex/assets/ll2.png

netex/assets/logo.png

netex/assets/positions/network-KroganSARS-CoV2.json

netex/assets/positions/network-PfefferleSARS-CoV1.json

netex/assets/positions/network-VirHostNetSARS-CoV1.json

netex/assets/styles/fonts/primeicons.eot

netex/assets/styles/fonts/primeicons.svg

netex/assets/styles/fonts/primeicons.ttf

netex/assets/styles/fonts/primeicons.woff