structural_balance : network graph: fixing NaN errors, showing only positive links
structural_balance : network graph: Increased charge on negative side and decreased link length. better grouping of clusters
structural_balance : network graph: Made slightly easier to switch on and off grouping
structural_balance : network graph: Made html_header and html_footer as functions
structural_balance : network graph: [Spike] Added cluster numbers for 1969 and 1999.