fixed IE9 again (it doesn't like font-size: 13 with no units)
fixed IE9 again (it doesn't like font-size: 13 with no units)

Fixes #11

martijnrusschen/radar-chart-d3,nagyistoce/radar-chart-d3,elaeon/radar-chart-d3,alangrafu/radar-chart-d3,Squarespace/radar-chart-d3,Hacker0x01/radar-chart-d3,Hacker0x01/radar-chart-d3,nagyistoce/radar-chart-d3,Squarespace/radar-chart-d3,elaeon/radar-chart-d3,martijnrusschen/radar-chart-d3,alangrafu/radar-chart-d3